Very nice, very easy (story mode)
The graphics are really good, smooth framerate too. Only in focus mode it seems to go less smooth. I think the sound is the best part of the game. Pretty much track (for a handheld) and good quality too. totally awesome.
The replay, I think thats one of the tony hawks series best quality. You allways have a score to beat. (I hope thats your's cuz the computer-highscores are not very high) The levels are pretty big too so thats no problem.
Finally, the WiFi. I didnt played online myself (i can't, I live in europe) but i guess that has to be good, only thing is: u can just play head-2-head (2 players) I think 8 would be more fun but 2 is nice too.