Ive been to this campground twice.  Both times were fairly full, but never totally full.  You can make a reservation, but you cant pick your spot until you get there.  Better to get there on the early side.  Some sites aren't great, so you dont want to be stuck with those!  There were sites with decent shade, and I liked there was a hiking trail down to the lake.  Also a pro that it isnt too far out of the bay area.