Lots of room, plenty of advanced terrain
crowded at times, lift ticket prices are insane
Breck is a great mountain. I've been here the last 3-4 seasons and it's a great mountain to board with friends. The trails are pretty diverse, so everyone can find an area to explore. Peaks 7 and 8 get pretty crowded, so stick to the harder trails on 9 and 10. Also try Lehman on peak 9, and any trail off of Falcon Superchair.
For the really extreme boarders try the runs off of the E-Chair and 6-Chair.