Bing referrals have increased on my site, but are still a long way from what you might call a tipping point (about 1/6 of total google.com + google.co.uk).
Also, I now use Bing by default, but on some searches Google is still better. Not for finding engine oil for my van this morning, however: all the Google results were for oil filter (did you see the word filter in my search? I don't think so!), so they are still doing their bit to help the tipping point along.