I tried the Trials trial the other day, then bought the full version this weekend. It's a ridiculously fun, addictive and super frustrating game. I'm digging it.
Saw this posted on another forum, and if it is to be believed, if you buy it now, MS will give you back 400 points. I can't find any mention of that on xbox.com, or Major Nelson's blog or Twitter, so I'm a bit sceptical about that. Still, it's well worth the 1200 points.