I wear regular bike shorts. Not bibs. Why? 1) I'm poor and can't afford the extra $$ that bibs cost, and 2)I don't really want to disrobe if I have to pee.

I realize that there are advantages to using bibs (like the chamois doesn't migrate), but I can't get past those two reasons for not buying/wearing them.

Pearl Izumi has drop-tail bibs with a zipper, if you're interested:
http://www.teamestrogen.com/prodPI_11211110.html