I'm not going to give away any spoilers in this article, but there is quite a bit for the player to unlock throughout the course of the game. And while the PSP version may not have the completely destructible environment offered by the PS3/Xbox 360, there's still plenty to blow up and toss around with the Force.
Holocron pickups throughout the game are viewable as artwork and concept drawings. Pay close attention to those holocrons, some may contain codes for unlocking additional skins or cheats.
As the game progresses, the player will have the opportunity to upgrade combat moves and Force powers, as well as customize the player's lightsaber and look. In Figure B you see the apprentice with the standard red blade of the Sith, but by finding crystals and hilts throughout the game, you'll be able to change the appearance of both.FIGURE B
The apprentice starts out with the recognizable red blade of the Sith. (click for larger image)
In addition to unlocking player skins, you'll be able to upgrade your Force powers. Ever since we saw the Emperor conjure lightning in Episode VI, we've all wanted that Force ability. In Figure C you can see Vader's apprentice hurling lightning at his foes, a skill he starts off with at the beginning of the game.FIGURE C
The apprentice hurls lightning at his enemies. (click for larger image)
Finally, there are the cheats. For some of the hardcore gamers out there, cheats are anathema; but I love them. There's a distinct lack of cheats with console games, period, so it's nice when developers leave them in. Most of the cheats in Unleashed are for unlocking player skins or upgrading Force powers, but there is a God mode cheat, which is only usable in Story mode.
The general consensus is that you get about six to eight hours of play from The Force Unleashed, but I think that's an extremely conservative estimate. Taking your time and enjoying the game, environment, and story in Story mode, as opposed to just running through and blasting everything, should yield around ten hours of play. Then there are the extras, which add a few more hours of play on their own.
What there isn't
Now that I've addressed what there is, I'll cover what there isn't; what isn't on the other platforms. As I mentioned, the PSP version offers features and content unique to, and created specifically for, the PSP. First would be the multiplayer. While it's not an infrastructure (Internet) multiplayer, it does offer an adhoc multiplayer. This means that if you know someone else, or up to three someone elses, that has TFU on PSP, you can fight against one another via WiFi in variations of Deathmatch and King of the Hill.
Speaking of dueling, that's another of the unique features offered on the PSP. There is a dueling campaign, wherein you square off against a variety of characters from the game and movies in one on one, and later two on one combat. Fortunately, your progress is saved when you die.
Another variety of multiplayer is Force Out, which is unlocked by completing the Order 66 mini-game. In Force Out, you attempt to force your opponent out of the ring by utilizing your various Force powers. In that respect, it's similar to a Jedi/Sith version of sumo wrestling.