Not a real common event, but I shoot in them whenever offered. One area club did a Progressive BUG Blast last year with a BUG event at every regular match for several months.
As you might expect, the biggest gun allowed does best. Things like Colt OACP, Glock 26, and 3" K-frame .38s. I did well in the BUG Blast shooting my Colt Government .380, second only to an Expert with a Glock. A friend with an old Colt Pocket .32 did very well, too.
Tough DA triggers and DA-SA transition on things like PPKs and Makarovs hurt their performance on the range.
Snubby .38s were pretty well out of contention.
We ought to do more. BUG matches can teach you a lot about your convenient hideout guns.