It will be interesting to see if Bing can improve on or even just sustain these numbers. It's inevitable that some folks will hear about Bing, try it once and decide it's not much different from Google and go back to their old habits. Others may just become converts though. As I've said before, even if Bing can steal a couple small points of share, that translates to many millions of dollars for Microsoft.
Update 6/17: New data from comScore today showing Bing's market share continuing to grow -- up to 16.7% share of searcher penetration and 12.1% of all search results pages.
Update 7/18: I'm tracking the latest search market share numbers in my post "Inching Along: Bing up a Fraction."