There are lots of different analyses of search share, but I try to be consistent and always cite data from a single researcher, so that it's an oranges to oranges comparison.
ComScore, the researcher I cite, hasn't released its search data to the public or press yet for the month of August. But it looks like it has made it available to Wall Street.
The results (according to a second-hand account from JP Morgan):
Microsoft is rolling out incremental updates to Bing on a monthly basis and is planning a bigger Bing update for later this fall.