For me, the Silver Lake Cyclocross course was difficult and technical. It had a very long (about 200 yards) of loose sandy beach and then a hilly forest section with plenty of off camber turns.
Here is a small portion of the sandy beach.
The sand was were I had the most difficulty. It sapped my endurance and made it hard to steer the bike. Because the sandy section was so long, I was unable to ride the entire section and had to get off the bike and run.
There was another obstacle that I though was very diabolical. After you finished the long run down the beach, you got back on your bike and did a short section of pavement which lead you around a building. Just as you came around the building, you encountered a barrier which was placed just before an up hill, single track section. So, after you were totally out of breath from crossing the beach, you ran into this lung busting up hill single track that, because of the barrier, you had to run. Killer!
For this race I got 5th in the cat 4 over 55 group.
Oh! by the way, it was a cool but very sunny day in Seattle and the Silver Lake Park was beautiful.