In a flash...
You'd probably be right, as I only got a friend's copy of this game and tried it out for a bit before giving it back to him.
In a word, it's simply another hand-me-down-game from the Console versions, and it becomes painfully apparent when this game fires up.
Gameplay
-------
Gameplay should and could be the incredible experience it is on the consoles. Lack of a HUD, intense graphical detail, quick thinking, but all these factors are severely limited by the PSP's technical and layout shortcomings (compared to the console versions). There are so many times I would've cried for a second analog stick to replicate the punching found in the console games. Also, a large HUD comes back into play, taking away some of the intense immersiveness from the console versions. There's a distinct lack of a first person adrenaline mode as well. The game's plenty fun, don't get confused on that; it's just not all it could be. Inclusion of an internet functionality was there to make this game a winner, but, to be frank, it's kinda broken. Kinda very broken.
Graphics
-------
Incredible. Just incredible for the PSP. However, ONCE AGAIN, it pales in comparison to it's console brethren. I might be a bit harsh in comparing it to systems that are far above it's technical limitations. There's just no going back from the 360 or even Xbox's dual analog and graphical superiority though. The game is incredibly detailed, but this takes a toll on the PSP, and causes some significant load times. Otherwise, this may be one of the most beautiful games to grace the PSP.
Sound
-------
EA knows music. 'Nuff said.
Final Words
-------
It's not that this game is bad, it's just that it's not as good as it could be. The broken online play and load times subtract from the experience. While the PSP version tries to mimic the motions by placing dodge buttons on the shoulders and more, it doesn't successfully capture the fluidity of using two analog sticks. The fun wears off after a few days, and then you just move on.
Unless you're a diehard boxing fan, consider just renting this game. After that, if you still find it incredibly enjoyable as a portable experience, consider buying it. However, if you own a console system with this game, BUY THAT INSTEAD. The console versions are much more polished, and sadly, the PSP becomes a (quite well done) hand-me-down.
In the end, once we try silk, cotton simply won't do.