Shannon and I biked to the grocery store tonight, and it was only sprinkling when we left, but on the way home it was like a typhoon! We're riding along, in the dark, on the wet streets, and rain was just streaming into my face. When I took a slightly deeper breath than usual, I breathed water straight up my nose -- that's how thick the water was on my face.
I didn't really mind getting wet, though -- I only minded the visibility problems. It was dark, as I mentioned, and the rain covered my glasses so that I had some trouble seeing past the lenses, and the rain coated the mirror on my bike so that I couldn't really see cars coming up behind me, and the general visibility issues made me a smidge nervous. Not terribly so, but just enough that the biking wasn't as much fun as usual.
It's good that it's raining though. I think I just won't bike in it unless necessary.