Don't have a cadence monitor, but I maxed out on the "ski-slope" start on the Tonbridge bypass once, at 44mph on a 95" fixed, which equates to just under 160 rpm. Was bouncing around and was really scary - only just resisted using the brakes. In spite of the fast start, my average at the finish was only about 22 mph.
On the bike I used for commuting (when I was working), I rode fixed (68")for a long time, but the route was up and down Kent's North Downs and was pretty wearing, especially on the descents, so switched to a single freewheel, which was much more comfortable and faster on the descents.