I wear leather or canvas-soled tabi almost all the time when we're working in the gym on-post. Despite multiple signs and verbal warnings by the gym staff, people ALWAYS track dirt in there, especially in the racquetball courst where we usually train.
On the mats, at home, always barefoot. Vinyl surfaced mats, though, easy to clean. And we're very small, so there's not a whole lot of feet we don't know ...
I get my tabi from a variety of sources, the best ones through www.budogu.com
(they may not appear on the site, you'll have to e-mail Peter and ask). Not cheap, but excellent quality.
I've also got a couple of pair brought back by friends from Japan, varying quality, depends on what you're willing to pay.
In wintertime, I use Sol Socks (www.solsocks.com/
) inside the tabi.
Several budo supply houses carry various tabi. In my experience, the rubber soled ones are good for outdoor training, but too sticky on the mat or on hardwood. The cloth-soled ones are a bit too slick on wood, work pretty well on the mat, useless outdoors. The leather soles are good-all around choices, providing a fair amount of traction and some glide on wooden or vinyl-covered surfaces, decent outdoors, if it's dry, not so good if it's wet.