I just raced my first crit tonight, and I have to say that I didn't think it would be THAT intense for the whole race. It was a heck of a lot of fun for anyone wondering if they want to take part in Midweek Mayhem. I'm happy to report that there were no crashes at all, so it seems to me that these are about as safe as a regular road race.
The only thing that I didn't really like was that I was in a 300 meter sprint for what I thought was 4th place, but was actually 6th due to a 2 man breakaway that I had no idea about...heck, I didn't even know what place I was in until someone told me that we had caught up to the lead group (which was actually the lead chase group).
So if you're a little tentative about these, take it from a rookie that they're not as bad as you're thinking and are a lot of fun and great training.