I moved to Egg Beater pedals several years ago after having a really bad mud clogging experience with SPDs.
I was at a race with a lot of sandy, peanut buttery mud. I was having a lot of trouble getting back in to my pedals. I had to stomp in as hard as I could, and my cleats would just barely engage.
Anyway, I was cruising up to a barrier, going pretty fast. I swung my leg over plenty early, preparing to gracefully dismount and leap over the barriers. When I went to unclip, my foot would NOT come out. I hit the barrier full speed and superman’d over it. I landed face first in the grass. I was lying on the ground, face down. When I picked my head up off the ground, my bike came down out of the air and again made me eat dirt. Good times.
You don't want this to happen to you! Some people spray the bottom of their shoes and pedals with PAM. I use Pledge, because of the lemony fresh smell. Both work. Try it next time you ride in the mud.