Since my business partner and I moved into our new office in March, I've been predominantly and visibly barefoot. Until now, I've been a bit cautious/self-conscious about it, since we're sharing the office with two other colleagues who don't know me previously and the fact that they seem a bit more "corporate-like" that my biz partner and I. Until today, no one had made any comments or given me any "looks", so I've been under the assumption it is OK.
I guess I my assumption was confirmed the other day, when one of the women working with us said to me this morning: "Moe, you're a bad influence. I think I need to start going barefoot too!" -- I told her to go right ahead. She didn't hesitate to kick off her slip-on heels and stayed barefoot for the rest of the morning.
She had a visitor right after lunch so, in the afternoon, she was back in her heels walking around the office. She pointed out to her visitor my bare feet as well – in a nice way though. The visitor (I think it was a potential client of hers, a nicely dressed lady) didn't seem to be bothered by my bare feet at all either and she commented: "you didn't have to put shoes back on for me, I'm not THAT formal myself"…
In retrospect, this is very similar to most of my experiences with barefooting at previous jobs/offices. I guess, for me, the fact that I don't make a big deal of my barefooting in the first place seems to do the trick for me.