The reviews said it was decent, theres no swimming and no flying vehicles, but i heard the multiplayer can be pretty fun. It's filled with lots of missions (though i've heard some are very similar or almost identical to the console version). There's bound to be a sequel, BTW let me know how it turns out, i've been thinking the same thing =)
It's pretty awesome, and with the cheat device made for the PSP, you can get flying vehicles; although, a lot of the build tops aren't painted (i.e. textured), so you get the neat flashy effect. You can also take screenshots, make videos (really gifs) by taking quite a few screenshots, change the speed of the PSP for literally twice the framerate in GTA:LCS, and more. Pretty awesome.
Speaking of making videos (gifs), here's one I just made:
It records every 8th frame, so it's a little jumpy X:.