I haven't actually completed the game yet, so this isn't a review. Instead it's just some rambling about the game.
The first comment has to be that Phoenix Wright: Ace Attorney: Trials and Tribulations is just like any other Phoenix Wright game that's been released on the DS. Astounding, I know.
But that's just it, it is simply more of the same. It's five new cases, using the same gameplay as the previous game without the special DS-specific case that the first Phoenix Wright game offered.
In fact, it's more of an expansion pack to the second game than a new game. The gameplay is completely identical. Literally identical: these are just new cases using the exact same gameplay as the second game. Yes, you get to take on a "flash-back" case as Mia but there's nothing different about Mia and Phoenix game-wise.
This game makes continuous references to the events in the previous games. If you haven't played the previous games, this game makes an absolutely terrible place to start. This isn't to say it's impossible: the first case does function as a tutorial on how to play the game, and they do use flashbacks to fill in details that might be missing.
But the fact remains that for the most part, the game play is identical in all the games, meaning there's little reason not to start with the first game.
If you have played the previous games and enjoyed them, by all means, pick up this game. But don't expect anything new, game-wise. This game is just more cases to play through.
That's not a bad thing: Phoenix Wright remains essentially an "adventure" game. It's all about the story and solving the cases. The cases I've played through have been the same quality of the previous cases. When I finish the game, I'll try and throw together a review, but I have a feeling I can sum it up:
If you liked the first two games, you'll like this one. If you didn't, you won't like this one. If you've never played any Phoenix Wright game, start with the first one.