If you’ve seen reports of Microsoft’s IIS gaining an increasing amount of market share, it’s mostly because of dormant/empty domains using IIS to host placeholder pages. In terms of actual active websites (as seen on Netcraft’s own data further down the linked page), IIS’s usage has been in steady decline and now holds around only 11%. Apache and Nginx are the dominant leaders here. Of course, as many know, you can use both Apache and Nginx together (ie. reverse proxy / load balancing).
Also with the whole using the legal system to seize other people’s domains thing, I wouldn’t trust them as far as I could throw them.
UPDATE: W3Techs has released their stats which don’t consider placeholder domains, only the top active ones. Overall in those, Apache is around 60%, Nginx aroud 20% and IIS aroud 14%.
“GoDaddy was using Apache (I assume on Linux) because it was a great technical solution. They didn’t switch to IIS on Windows Server 2003 for any technical reason. The switch was accompanied by a press release by GoDaddy, containing Microsoft promotional language. Now, I’ve changed many servers from one thing to another, but I’ve never made a press release about it. GoDaddy wouldn’t be doing that unless Microsoft had offered them something valuable in return.”