While the occasional move doesn't work perfectly, most everything is timed to a tee. Repeatedly pressing the turbo button (a new addition to the series) makes your thumb extremely tired, but its a cool option that really helps as the levels mount.
The level designs are all great, except for the last level, which is a re-hash of a previous PS2 downhill level ("The Dam", here referred to as "Hoover Dam"). The music rocks - and its a true pleasure to hear real licensed music in stereo sound coming from the DS - the Green Day track is a personal fave.
All-in-all, an excellent addition to my DS library. If you're a fan of TH, snowboarding, or racing games - pick this bad boy up! 9/10