This is probably one of the most underrated series out there; it's a real hidden gem. Most might bypass it because it looks like a magical girl series. But no matter who you are, take time to watch all three seasons of this; you won't be disappointed. It's been said that Nanoha(the character) is one part Sakura (from Card Captor Sakura), one part Goku (from Dragon Ball), and one part Gundam. Seriously, the producer is a big Super Robot Wars fan, and the color scheme of Nanoha's magical girl outfit is a direct shout-out to a gundam. Her Goku reference comes because she tosses out magical energy blasts as if they were going out of style.
Nanoha starts out seemingly like standard magical girl fare. Girl finds a wounded magical animal, and gets her powers from it. She spends the first couple of episodes sealing Jewel Seeds, which go out of control and create monsters. Then she meets Fate, a rival magical girl also trying to collect the Jewel Seeds, and things start to change. In fact, right around episode 7, you get two plot twists that hit you out of nowhere, and really let you know you're starting to watching something different. Although if you were watching carefully, you can see hints of them coming.
It's hard to talk about the story without spoiling those plot twists, so I'll just say that you won't be dissappointed. It's often been said that Nanoha is really a Gundam shonen story, but with magical girls. I'd have to agree with that.
In a word: Beautiful. Besides 4 transformation scenes that happen in the first 5 episodes, Nanoha doesn't make use of any real stock animation scenes. There are a couple others, but they are so minor that it doesn't really matter. Everything else is rendered individually. While most magical girl battles consist of stock animation footage as girls toss their attacks back and forth, Nanoha and Fate are much different. They may call out some of their attacks(or their intelligent devices do), but they are busy ducking and weaving through the air while they do it.
Some of the music may take a bit to grow on you, but most of it matches and enhances the moods perfectly. In most anime, I don't notice the sound or background music much, but here it really stands out. One of my favorite tracks happens during the tenth episode, as Nanoha fires off one of her famous Divine Busters.
As mentioned above, the characters are the real draw to this, especially once Fate is introduced, and you see her situation. Even side characters get a bit of depth to them, although the main story is between Nanoha and Fate, with a bit less towards Yuuno. And some people claim that Raging Heart and Bardiche are main characters in their own right. You'll have to watch to see for yourself (especially during A's, the second season).
One major notable difference, is that Nanoha isn't a whiny crybaby like most magical girls. She doesn't get real conflicted when facing tough circumstances. On the contrary, she's glad she got her powers, and is ever willing to step up and do what needs to be done. Yuuno, her ferret friend, attempts to tell her once that it might be too dangerous, and he'll collect the jewel seeds on his own. She stops him the middle of that speech, and tells him "I'm sorry, I can't let you do that. If it's within my power to help someone, I'll do it." And if she has to beat someone down to get her point across, she'll do it.
The one minor draw, is sometimes it's hard to believe this emotional maturity is coming from a nine-year-old girl. But I have to admit, such an attitude is a refreshing change of pace from most magical girls who whine and cry, wishing they could be normal, getting afraid of each new dangerous situation, andwanting someone else to save them.
Magical Girl Lyrical Nanoha is really a prelude to the series. The first season here starts out almost like a standard magical girl series, but halfway through, it takes you on a wild offshoot that feels more like a shonen series, but with more emotion and heart. It's when you go on to watch the second and third seasons, that you really see what makes Nanoha different.
Watch it, and you'll begin to wonder too, why this is easily the most missed and hidden gem of the anime world.