In reply to After Eight: It's something I've never really tried.
I don't get the whole slimy inners because after using my shoes I hang them up in my cupboard with cedar blocks inside, which help keep them from ponging, and helps dry them out.
Feet wise, I find that treating them like my hands (intense cleaning daily, sanding off dead skin, ex foliating or whatever these boffins like to call it and moisturising after a climb.) Usually means that I don't really have the rotten smell wafting up although the gf does find it hilarious my regime is more extreme than her's.
I'm not a high grade climber by any form, but I suppose old habits die hard, my old man never wears socks, so I followed suit, and he didn't pay half as much attention to his feet as I did mine. So I guess my standards are pretty low, seeing as the first proper pair of shoes were hand downs from him.
Either way it's down to personal preference, I climb without because I've always climbed without, I don't suffer from raw skin or anything, so I have no real reason to swap to something else. But if I see someone wearing socks I don't pull a funny face and mumble about them being an amateur, for the exact reasons mentioned about, some of the greats wore/wear socks, some didn't. But if you're comfortable and having a good time, it really doesn't make much difference.