If you were a fan of the original series (http://www.imdb.com/title/tt0140644/), the 2199 series will be a nostalgia filled experience. There have been a number of updates as other reviewers have posted. The end result is that 宇宙戦艦ヤマト2199 is overall a richer experience and up to par with today's expectations. If you are someone who has never seen the original, this is an exceptional piece of work and fully stands on its own without need for prequel.
If you're a fan of the original soundtrack, you're in for a special experience as the most familiar melodies are there and unchanged. You will also find a plethora of new material that blends well with original 1970's compositions.
The animation is clean and crisp, but full of detail. Typically not what you'd expect to see in a weekly televised series. Due to the unique method of release (episodes grouped and released to theaters first and shortly after broadcast episodically), the production values are very high.
Again for those familiar with the original series, everything is updated but familiar. Nothing went through a redesign so drastic that it would not be recognized. Character designs are updated to more contemporary appearances. The mechanical side of the designs benefit most from the improved animation technology available today. Some elements and characters are new, mostly done to complete the story or add depth. The story is now deeper without becoming mired in its own twists and turns hopefully allowing the viewer to become more emotionally invested with at least a few of them.
The end result is a remake that does not need to rely on nostalgia but embraces and honors its past all while bringing the animation, sound, and story into a more contemporary era.
