I picked up this series on a whim, and I am very glad that I did. It shows off the fruits of having both a good concept and powerful execution; as a result it is, in my opinion, one of the top anime of 2011.
Steins;Gate relies heavily on the concept of time travel within various parallel worlds, referred to as "world lines." Essentially, a small group of high school and college age students that create a machine capable of sending text messages to the past. They develop and encounter various other time travel devices as the series progresses. The series ties into the 2000-2001 John Titor posts fairly neatly.
The story has a fairly slow beginning, lasting roughly through episode seven. While an initial hook--the stabbing of a main character, Makise Kurisu--is provided, some may accuse these early episodes of plodding along. Due to the absence of an antagonist, the writers rely on various mysteries surrounding the time travel machine to move along. I found that these early episodes were valuable for character development. Once the series picks up later on, it is unlikely that the writers could have inserted appropriate time for said development.
Nevertheless, it is slowly revealed that an evil organization is also working on a time machine. While the shadow of this organization hangs over the entire series, it is not the primary focus. While we see the organization's minions, for example, their leaders and overall structure are never challenged. The thread that occupies a much larger chunk of the story is the use of D-mails (text messages to the past). These D-mails have drastic effects on the progression of time that only the protagonist can remember. Some of the changes they cause are good and some are bad, but eventually things reach a breaking point.
Another series concept comes into play here: the attractor field. It essentially means that nearby parallel worlds (world lines) will tend toward a similar result unless one gets far enough away. This means that the main character has a difficult time avoiding a painful future. The mid to late section of the show becomes somewhat desperate in tone as the protagonist tries to undo his various mistakes and secure a happy future. Due to certain plot events, viewers with a short attention span may find this section boring because of its repitition. I would encourage these viewers to examine how these episodes drive home the hopelessness of the situation.
All of this builds up to a climax that is not quite a visual spectacle, but suitably intense all the same. The ending ties up loose ends well and left a pleasant taste in my mind.
The character designs of Steins;Gate feature fairly rounded faces and (barring Feyris) realistic hair colors. The body proportions are also reasonable. The color palette used, suitable for the series' tone, is not exploding with hot pinks and reds.
There are no shounen-style fight scenes, but the crowds at least seemed well animated to me. In at least one case the animation style shifts to emphasize a particularly intense moment. Characters are also expressive, particularly in close ups of the main character.
The opening and ending songs were not exceptional to me, but they also weren't terrible. The animation of the opening might give unsuspecting viewers a seizure if they aren't careful, while the ending is just the opposite. I found the slowly reassembling hourglass/pocket watch of the latter to be somewhat boring.
The Japanese voice actors, however, are spectacular. I have a feeling that even viewers who don't speak Japanese will be able to appreciate the various intonations of the characters. The main character's seiyuu in particular impressed me, whether he was arrogantly yelling "CHRISTINA!," muttering to himself on the phone, or debating the current dilemma.
One mark of a good character is changing goals. The characters of Steins;Gate have this and more: changing emotions, states of mind, and relationships that move at a satisfying pace. The main character, Okabe Rintarou (Okarin), is one of my favorites of all time. He is quirky and charismatic, yet when the time comes his character also has excellent depth. All of his strange habits are tied to deeper psychological motives and he has realistic reactions to the various incidents that occur.
Daru's character, while not terribly original (i.e. fat, college age hacker), has a number of memorable quotes. Some may find Mayushii, the protagonist's childhood friend, to be annoying and stupid. While her character is not as impressive as Okabe's, she at least didn't annoy me severely. Makise Kurisu, the heroine, could be labeled as a standard tsundere. She is a favorite of mine despite this.
Overall (8.5/10, Excellent)-
Steins;Gate is must-watch for anyone interested in anime more complex than your standard shounen or magical girl fare. The concepts may be difficult to grasp at points, but the story is well worth it.