Ars Technica has some interesting browser market-share numbers.
By most measures, Internet Explorer is losing ground. Depending on whose numbers you're looking at, Safari and Firefox are either holding steady, or gaining.
Just to bring a splash of reality to the WebKit triumphalists in the comments in a related article on Ars, Safari's growth -- even in the rosiest measure -- is 1.7% in absolute figures. The chart shows a 56% percent increase -- but that's relative to its original tiny share.
I actually think it's good having more than just two mainstream browser choices. I'm impressed by what I'm seeing with WebKit, particularly with the speed at which they seem to be fixing all the stupid issues that make developing for Safari 2 so excruciating. It will be interesting to see if Safari can crack 10%. Support for other OSes, while maybe a bit far-fetched at this point, would be a sure-fire way to see that happen.
Lastly, it's also worth noting that the introduction of IE7 hasn't done anything to staunch the steady drip-drip of market share away from Explorer.
Microsoft still has an enormous amount of catching up to do there. IE7 isn't bad, but with all the superior alternatives available, just being Microsoft and being not-terrible just isn't compelling enough. Frankly, I don't think Microsoft can succeed at producing a really killer browser until they resolve all the internal corporate angst about it undermining the monopoly power of their OS.
I'd like to think they can pull it off, but it's so ingrained in their coporate DNA, you have to wonder.