I love it. I've got mud in my blood, I tell you!!
I have disc brakes, and when it rains around here the temperatures are usually pretty warm. Sometimes in the summer a cool shower is much appreciated. The only thing I dislike about it is the extra cleanup I have to do. But other than that I think riding in the rain is awesome, provided its warm outside. I won't commute in the rain at all, either. But for leisure rides, I think the mud makes things alot of fun.