It seems much, much faster than my cable provider's (Cox). I changed during the summer, I think, when it often seemed to be taking several seconds for each name resolution.
Dunno if there are any issues in using such a service, but I figure I'm such a small-fry that it's not much to worry about. At least so far...
I just noticed that Google has a free public DNS as well - http://code.google.com/speed/public-dns/
Cheers,
Scott.