Hitwise released their April search market share report and comScore released theirs.
Both sources say that Bing powers just about 30% search market share (between Microsoft and Yahoo properties together). Hitwise says Google dropped in market share, whereas comScore says they have grown.
Here are the quick snapshots:
Hitwise:
comScore:
A WebmasterWorld thread, which is a very pro-Bing forum these days, talks about how Hitwise numbers are right.
Forum discussion at WebmasterWorld.