I did CSS Level I yesterday, and wanted to fill in my review, my impressions, etc.
First, I had a blast! It was great fun riding the track. Second, I really honestly made some great improvements in my riding skills. Yes, in just one day. I actually surprised myself at some hidden potential that I just needed to coax out. Keith and Dylan's instruction was excellent at presenting fundamental information and skills which you can directly apply and see instant results and improvement. It's easy to understand, without being over simplified. Maybe that's the point, that these skills are simple to begin with, but not always obvious. Also, they are both very charismatic and keep everyone engaged.
The class format alternates between classroom seminars and track drills. In the seminars, they present cumulative skills that you build upon and apply in the drills afterward. These are not complex which makes it easy to go out and apply them immediately. Things like throttle control, entry points and proper turn-in, good lines, etc. Each time I went out I felt it coming together even more.
During the on-track drills, a coach follows you and notes your application of the skills and where you need improvement. Then he has you follow him for a few laps and shows you what to do. Afterwards you get one-on-one coaching. It was very helpful for me to follow the instructors. And when everything clicked, and I really nailed a few laps, it was a really great feeling.
As for the school itself, it was very well run. Everybody involved in the school was very professional and very skilled, and at the same time very approachable and friendly. They also provided plenty of food and kept everyone well hydrated as well, so you really didn't have any worries or distractions during the day. Just show up ready to ride and learn.
I rode one of the school's bikes, and got along very well with it. It was set up well and handled great. Stable and confidence-inspiring.
Overall I had a great experience and am looking forward to doing Level II. I may even do Level I again some day at a different track if the opportunity comes about. I think I improved as a rider more yesterday than I have in the last year of canyon riding.