Improves so much on the original that I think I wet myself.
1. Not enough variety.
2. AI sucked balls.
3. Snipers killed everything.
4. CIS was overpowered; droidekas almost impossible to kill especially against "special" AI that ran out and fired
5. AI again
Oh man. This fixes most of those problems. First of all, the balance issues are fixed. Not only do snipers not kill everything anymore, but normal troopers can now kill stuff! Problem 4 is also solved; a player needs to get a certain number of points now to get the awesome classes. There's a new class on each faction, too. The commander faction. Usually they're good on their own, but they also have a one-shot group "buff" that improves the squad as a whole. Great new element.
Oh, and all the new game features... Hero characters are a blast to play as, under normal circumstances. You really feel like the hero you're supposed to be, especially when you enter a room and enemies start shouting "Get skywalker! etc". Then you flip the hell out and kill them all. It's glorious. Of course, you may get unlucky... sometimes you can't find enemies, meaning that you lose health and die. Sometimes you get killed cheaply by an enemy in a tank, or an enemy with a rocket launcher. Still, they're great.
Space battles are great, too. They take a lot of practice, but once you've got the hang of it, it's fast-paced and fun. Well... except for the fact that no enemies really put up much of a fight, but that's for the next section. You can quickly and efficiently disable the enemy capital ship if you have a good partner. After going inside and taking out shields/auto turrets, you can co-ordinate attacks to make sure that your opponent's ship is crippled before they know what's happening. Extremely satisfying.
Now for the bad stuff... in the original, every planet had at least 2 battlefields, and some of the best ones have been cut. Bespin: Platforms is gone, but that's okay because now you can have even more ships flying in space. However, the fact that Naboo Plains is gone means that Naboo is just boring. Some other maps suck, too.
And the AI... while improved over the original (they use grenades and use cover), it's still total crap (they use grenades on YOU when you're a jedi, as well as when they're still behind cover). Once you get to be moderately skilled, enemies offer you no challenge except for in those levels where your team sucks SO badly you'll lose unless you kill 50 enemies in 1 minute. This happens far too often.
Lastly, the two new gamemodes (hunt and hero battle aka Assault) aren't that well done. Hunt, where a "weaker" team has to survive for 5 minutes against greater numbers, works sometimes, but others are just pathetic. To take hoth as an example, the prey can have no trouble taking out the predator. Wampa vs Rebel: Who will win?! If they fixed this, it would be better. Also, while the hero battle is fun, the Villain power Force choke is broken, and the hero battle option is only available in Mos Eisley.
Buy the game. You won't regret it.