Hitwise has released their search engine share data for the month of June 2009. This is significant because it's the first month that Microsoft's Bing.com has been around. Of course, it essentially took over for Live.com, so there are a few factors to look at.
Now, normally we wouldn't look (or even get) the week-by-week data. But that is quite possibly the most significant for this particular month. As you can see, Bing saw growth every week in the month of June.
But when you average the weeks together, Microsoft search engines still saw a slight loss year-over-year. This contrasts the data from the less authoritative Statcounter, which was released July 1.
Still, it's no doubt who's still sending traffic by way of search referrals: Google.
Perhaps overall search referrals would be higher if only searchers could really find what they're looking for. The keyword length is on the rise, possibly indicating that searchers really have to do a lot of work to find what they're truly searching for.