So the game is, on the whole, a close approximation of its console siblings (the major difference is that the graphics, while good for PSP, are not nearly as good - as expected for a PSP port). This means that it shares its flaws, too. Collision detection, AI issues, clipping - pretty much everything that afflicts the PS2 version also afflicts the PSP version (more so in some cases).
Last year, there were three decent PSP-exclusive mini-games, but those have been ditched in favor of a new mode called "Road To WrestleMania," which, contrary to its title, is not just about going to WWE's premiere show; it's actually where you can create various tournaments to go for a title or to become King of the Ring. The developers wanted a mode where you can quickly start playing while on the road, but it's not really all that necessary since you can easily set up an Exhibition match if you want a quick wrestling fix.
The one thing that we really miss is the connectivity between the PSP and PS2 versions. It was a great idea to have one set of data that you could either play at home or take on the road with you. Now, you're left with little choice but to start from scratch, even if you've invested countless hours in one version or the other.