At least on Portal Forums.net, Internet Explorer 7 this month took the lead from IE6.
Internet Explorer 7: 117373 hits which makes up 36.6%
Internet Explorer 6: 111058 hits which makes up 34.7%
Firefox 2: 21953 hits which makes up 6.8%
Firefox 1.5: 34848 hits which makes up 10.8%
I don't know what happened with Firefox 2, last month it was 10% exactly. Firefox 1 last month was 7.4% so it looks like we saw a shift backwards within the Firefox camp.