engine - 4:04 pm on May 3, 2011 (gmt 0)
Web Browser Market Share and Analysis [arstechnica.com]
April was the first time that Internet Explorer 9 and Firefox 4 were available for the full month, making it the first chance to really get a feel for how rapidly users are switching to the new offerings—and the first opportunity to see if compelling new versions are able to halt Internet Explorer's market share slide, or spur new interest in Firefox.
Both Microsoft and Mozilla will be disappointed to learn that so far, nothing much has changed. Internet Explorer is down yet again, dropping 0.81 points to 55.11 percent. Firefox experienced a small drop of 0.17 points, to 21.63 percent. Chrome was up 0.37 points to 11.94 percent, and Safari was up 0.54 points to 7.15 percent. The implication from this is that the new browsers, though both substantial upgrades over their predecessors, are doing little to attract users of other browsers; the people switching to them are merely upgraders.
It's worth reading this article, imho.