Disclaimer - I don't race but plan to some day.

If you want some objective speed information, that also shows the surges, sprints, etc. go to connect.garmin.net. Click on Explore->Activities. You don't have to have an account to do this. Zoom the map to a location you know had a crit recently, has one weekly, or had one at some time in the past. Change the filter to limit the results to cycling. Then hit search.

Depending on the crit it is very, very, likely that someone had a Garmin of some sort and downloaded their data to Garmin Connect. Sometimes the titles tell you the cat (or if you download the race flyer you can figure it out by the start times). Sometimes you get lucky and the racer writes a bunch of notes about how they felt, how they finished, etc. Often multiple people from the same race had Garmins and uploaded their data so you can see comparisons. If it is close to where you live you can ride out and do a few laps solo just to get a feel for the track and then look at the Garmin tracks again. If you look at the speed chart in Garmin Connect just remember that there is some pretty severe data smoothing going on there that affects how the charts look visually. You can even download the file and look at it in a program that allows more detailed review like SportTracks where you can see the speed surges in more detail and can turn off the data smoothing.

Anecdotes are good and certainly have their place, but if you want reliable, objective, speed data (and understand that, as gets pointed out ad nauseam, speed is only one part of the equation) you can't really beat GPS data. If you get really lucky there might even be a power track that you can look at on one of the files you find.