Can be snow-covered, December through March.
Beaver Creek is a motorcycle trail and has a number of whoop-dee-doos and berms, which have been burned in by motorcycles and are fun to rip on a mountain bike. The area recently burned and is currently closed to motorized users for 2015, but open to mountain bikes, so it is nice and quiet out there.
The last part of the trail is very scenic with aspen groves and some great rock formations. There are a lot of great places to stop and take in the canyon.
The trail can be loose in the fall and there are some deep water crossings in the spring, but that is part of the fun. That said, be prepared to get your feet a little wet as you rip down this singletrack trail through the mountains.
There are lots of connecting trails around that can be used to make this ride into a loop.