One of the biggest problems is that the vast majority of the cast is brushed aside in order to make room for three brand new villains. Of the nine protagonists in Final Fantasy VII, Cloud is the only one to receive more than token scenes. Tifa, Aries, and Vincent have more than bit parts, but Cloud is still the focus of most of those scenes. The rest of the cast shows up at the end to assist Cloud in a fight (which is just a summoned monster; not even a significant antagonist), but it is far too little and far too late into the movie for their appearances to have any meaning. In the final battle the rest of the characters don't even join in Cloud's fight against his nemesis because the writers decide to invoke the "this is something he must do alone" BS.
That said, the fight scenes are all excellent. There are fights spaced throughout the movie, and one of the best ones is actually between Tifa and one of the villains. All of them are ridiculously over the top by movie standards, but exactly what one could expect (and hope for) from a videogame. In this sense the transition from game to movie actually worked very well.
The plot was alright, as long as you're expecting an epilogue to the game instead of an independent plot on the same level of the game. Cloud has regressed to his mid-FFVII level of depression and isolation, but he is eventually dragged out of it by all of his friends and pulls himself together in order to save the world once more. His regression is understandable to a degree, but it is also annoying to watch considering how he was fairly likable by the end of the game and then we jump right into him being at a low again.
It doesn't help that they bring back two characters that, by all reason, should have died in the game (and no, not the character whose death everybody already knows about) with absolutely no explanation They even go so far as to have Cloud interrupt one explanation, which just leaves the audience hanging.
The amount of exposition is incredibly unbalanced. They start off with several minutes of exposition reviewing the plot of FFVII as well as what has happened in the interim. Unfortunately it isn't enough of an overview for people new to FFVII to catch up, but far too much for dedicated fans who end up bored by it. Then, other things which both fans and new viewers need to know, they gloss over or ignore completely.
If you haven't played the game then watching the movie is only going to leave you confused since it is expected that you know the entire plot of the game and are familiar with all of the characters. Two minor characters from the game, Reno and Rude, have significant roles in the movie, both in terms of plot progression and as comic relief. They do provide a few humorous moments without coming across as stupid or inappropriately goofy.
The sound and visuals are absolutely outstanding, and will serve to make fans even more eager for a PS3 remake of the original game. They are top of the line CGI, even years after the movie came out. For the most part the characters look like they were taking out of the game and had they're polygon counts increased by a factor of eleventy zillion. There were a few cosmetic changes, such as giving Tifa a new outfit, all of which worked out for the best.
The soundtrack is equally as impressive, and the remakes of tracks from the game are all better than the original. The tracks not only sounds great on their own, but fits into the scenes where they are used.
The translation was pretty good, for the most part and the voice actors are all excellent and sounded appropriate for the roles then were given. As can be expected, there are certain things that just don't have an exact Japanese-English translation, such as when Aries is being dismissing of Cloud's angst-fest by saying something nonsensical. Both the subtitles and the dub work well - the only problem is that they don't match up in many instances. About half the time there are discrepancies, the sub is better and the other half the dub is better, so nobody really wins that one.
Overall, it was a good movie for the fans as long as you aren't expecting too much from it. It had enough of a story to be interesting and had the fight scenes that fans were looking for. It just could have been a done a little better and Square-Enix should have done a whole lot more for viewers who either haven't played the game or played it so long ago that they didn't know the story inside and out.
