I have only been there twice - The 1st time it rained the whole time, so we rode through tons of mud and it was cold! I wanted to cry. The 2nd time I went with no sleep the night before, so I hurt the whole time. I've yet to try it in ideal conditions, but I do know enough to know it's worth the trip.
I've been there once. Its a lot of fun - some good climbs and downhills, nothing that technical, but a good, long, fun ride.
I'd suggest starting at the bridge and running the loop around the lake counter-clockwise. That puts you at the ranger station about 2/3 of the way through the ride - only place to refill your camelbak/water bottles.
There is a 24/25 mile loop and a 30 mile loop (or maybe 32 miles??). Basically there is a point when you have to decide... cross the street and do the full 30, or continue on the loop and just complete 24 miles (JUST 24 miles ).
a friend of mine lives 5 minutes from there. ride it about twice a month. definatly worth what is a 1.5 hour ride for me. last weekend was a little hairy in the snow. not so much the bike riding but we decided to take an un-mantained section of road about a mile and a half back into the woods and start from there. they are some nasty hills when covered in compacted snow and ice. learned how to use the downhill descent feature on my truck real fast. think a little pee came out none the less.