Usual disclaimer: data is just for that site, but they keep old numbers up that show trends VERY well.
IE as a whole still is still showing major decline, with IE 6 and 7 gowing downhill at about the same rate.
Opera and Safari are flat at low levels. Firefox is flat at a high level.
Chrome and IE 8 are both rising.
The pool of IE6 users represents XP machines that have not been upgraded. It cannot realistically grow larger. People who have not upgraded from IE6 probably never will on their current machines; the decline of IE6 is likely caused by old machines failing and new ones (mostly Win7/IE8) being bought to replace them.
IE8 is thus rising, but I don’t think they are getting almost any converts from non-IE browsers. Watch for each successive IE release to be weaker than the last.
Chrome is scooping up users left and right. The net effect is that they are taking away IE market share, but I’m going to speculate that a good number of people are still switching to Firefox, while others switch from Firefox to Chrome, with an overall effect that Firefox is flat.