If you're going into this Animation hoping for a really good story that makes a lot of sense, you're going to be very disappointed. That isn't necessarily a bad thing though, especially with Hyperdimension Neptunia. Also, if you are going into the Animation without having played Mk2 or Victory, there is a good possibility you may or may not be confused, as the Animation does sum up / play out stuff from those games. Watch the OVA as well so any loose ends from the Animation get tied up.
I'm by no means great at reviewing Anime at all, but decided this would be my first one, and the reason why I even checked this out in the first place, was because Hyperdimension Neptunia Re;Birth 1 was coming out on Steam, and I thought it would be a good Idea to watch the Animation first to get a feel for the characters.
To get a good example of how the Story for this Anime is, it's pretty much revolves around four CPU (Console Patron Unit) Goddesses that come together to declare a Friend Treaty, in order to stop the Console War. Yes, I said it. Console War. That should set you off already not to expect a serious story, because there is a lot of Gaming / Movie / Anime references mentioned throughout it, a good amount of 4th Wall Breaking, and just when you think the Story starts to get serious, the Characters in it (which are fully aware they're doing all this) break away from the seriousness quickly. There is also a lot of Fan Service involved, which you may or may not like.
Even though it wasn't a straightforward story of what is going on, I still give it a 8. It took me until Episode 4 to actually get into it, but when that happened, I couldn't stop grinning / laughing like an idiot from time to time every episode.
Animation Wise, I give it a 9. Sound Wise, about a 7. It's actually kinda tough for me to talk about the Animation and the Sound, since it's harder for me to focus on any thing that isn't the Story or the Characters (Kill La Kill's the only exception, because I loved the Music from that.)
Characters... Oh dear... What's a good way to put this...?
For me personally, I put it this way: It is very hard NOT to like any of the Characters. As far as the goddesses go, they have their own interests, whether it revolves around reading, Gaming, or Cosplaying.
You have Neptune, known as Goddess Purple Heart, the CPU of Planepture. She resembles the Sega Neptune (which was cancelled.) She is the main protagonist in the Animation, and she's well... a very lazy and Ditzy character, who is serious when she needs to be. Her being ditzy is not a bad thing at all, because she is mainly the one that will keep the Story from being an actual developed story.
Next is Noire, known as Goddess Black Heart, the CPU of Lastation. She is based off the Playstation. She is a VERY Good example of a Tsundere character done right, and it's hard not to like her, even if she can be incredibly cocky toward the other Goddesses.
Afterwards, you have Vert, known as Goddess Green Heart, the CPU of Leanbox. She is based off the Xbox. When I mentioned Fan Service earlier, Vert is your go-to Goddess for that, since over the other goddesses, she has the biggest.... features. She's extremely intelligent, but she lets her said Features get to her Ego often, so she uses it to her advantage over the others.
Finally, you have Blanc, known as Goddess White Heart. She is the CPU of Lowee, and she is based off the Nintendo Wii. She likes to spend her time Reading, and keeps to herself mostly, but oh boy, if you do some thing as much to piss her off, you will regret it. She can easily switch from being calm and collected to flat out vicious, and her lack of "Features doesn't help with it either.
I'm sure you can take a guess what I mean by "Features." Their "Features" are essentially an indication as to the Hardware their respective consoles had at the time (which is odd for Nepture when you think about it, since the Sega Nepture never saw the light of Day, yet her CPU Form definitely isn't lacking Feature wise.)
Then you have your other characters, the CPU Candidates, and the younger sisters for some of the Goddesses.
Nepgear is Neptune's Sister, and she resembles the Game Gear. Attitude wise, she is about the same as Neptune, except that she is more serious and innocent than her sister, which makes her very loveable with how she can be during the animation. In the Games and in the Animation, even though she is younger, the characters mock Neptune by mentioning how they like her sister already, and that she is an improvement compared to dealing with Neptune herself.
Uni is Noire's Sister, who resembles the Playstation Vita. She is also innocent, and can be a bit of a Tsundere herself, but she mainly cares about striving to perform as well as possible so she can be thanked by her sister.
Finally you have the twins, Ram and Rom, Blanc's sisters. Ram closely resembles Blanc in terms of her personality, and that makes her the more dominant of the twins, while Rom resembles Blanc in terms of her physique, while she mainly keeps to herself.
Vert herself does not have a Sister, since Microsoft did not have a portable console, and throughout the Games and the Animation, she shows how much it bothers her for not having a sister of her own, but that doesn't stop her from trying to take the other Sisters, which can be funny (and involves fan service.)
Afterwards, you have some Sub Characters.
Compa is Neptune's first actual friend that she meets in the Games, and she resembles Compile Heart. She focuses on trying to better her skills of being a Medic to help the ones she cares about, and she is incredibly innocent, while her Weapon is a giant Syringe... but from time to time has a sadistic side to her (In the Games, she mentions that if some one is annoying her too much, she can just poke them and inject them with a quick burst of Air to "silence" them.
IF is Neptune's second friend, who makes a living by working with the Guild to take on missions, and she resembles Idea Factory. She has a more serious tone compared to every one else, but not only can she not remain that way for very long because of Neptune, but she has a fairly prude-ish side to her as well.
Plutia is the CPU of Planepture in the dimension her and the other character come from, and she is known there as CPU Iris Heart. Personality wise, she is very kind, but also very slow, and it makes you wonder what is wrong with her. Honestly, I did not like her very much as a result of this. She reveals to her new friends that she doesn't transform into her CPU Form very often, because Histoire in her Dimension advises against it... for a VERY good reason when you find out shortly after that. She's okay, but her CPU form is mainly what lets me tolerate her as a character.
Peashy is also from the same Dimension as Plutia. Not only is she cocky, but she is a good example of what it's like to actually have a much younger sister, when they have to try to one-up you or take things from you, or get you to play with them. Peashy is pretty much like that, which makes her interesting, because Neptune has to suffer as a result since Peashy stays with her for a while. Stuff happens throughout the plot that makes her the focus of the second part of Hyperdimension Neptunia that is hard to get into detail about without throwing out some major spoilers, so you will have to find out for yourself.
Finally, you have your Antagonists. I actually won't list them off / go into detail about them. You will have to watch for yourself and judge how they are.
Character Wise, this is definitely a 10/10 for me. Even though the characters all have different personalities compared to one another, the way they just act through all 12 Episodes (including the OVA if you decide to watch that,) makes you not only never take them seriously (there are serious moments in the Story though,) but it will make you either love most, if not all of them.
For me personally, I rate the Animation overall as a 9 / 10. With a Satirical / constant awareness and 4th wall breaking by all the loveable characters in this, it would be hard not to recommend this to friends, especially if they are thinking about trying the Vita Remake of the first Game that came to Steam recently. While the Story can be confusing for a bit, it definitely picks up in the 2nd and 3rd part of it, and that's when it gets much better.
Not only did I really enjoy this, but I also can't stop playing Re;Birth 1 on Steam. It makes me hope and look forward to the rest of the Games coming to Steam eventually (Re;Birth 2 and Hyperdevotion Noire was confirmed recently for this year.) This is an Anime you would want to watch before you start on another Long series, and it's also an Anime (if you like the Games) that you will want to watch often. Makes me very sad though that there is not 2nd season for the Animation ;_;