IIS 7 is positioned exactly between a rock and a hard place. Its bundled in with the more recent MS Server Products (2008+), but sadly will not install on Windows Server 2003. This is the crux of the matter that unfortunately puts IIS 7 out of reach.
Developers want to work with the most recent technologies. This is seldom possible in the world of Windows development in 2010. In a distributed SOA environment a great deal of customers are still using, yup you guessed it – Windows Server 2003.
Lets say you have a web application, and you install this at your customer sites. Assuming you have more than 1 customer, and hopefully more than 10, a problem will quickly come to light. If just one of your customers has Windows Server 2003, your web app needs to be compatible with the version of IIS that ships with Windows Server 2003, yes ladies and gents IIS6. You cannot assume any of the advanced features in IIS7, you have to code for worst case scenario right? You can’t ship a feature if the client’s server infrastructure doesn’t support it.
The situation gets more cynical when you realize that even without customers, you should infact plan for the worst case scenario. There is still a wide client audience running Win 2k3, hence IIS6 becomes your target web server.
Its 2010 and clients still don’t want to upgrade past Windows Server 2003. Can you truly blame them if Win2k8+ provide no real business value and induces additional costs. Linux outshines Windows in this regard, there is no political motivation to bundle in web server versions with OS version.
The longer I ponder on this article, the more I realize that to a great many developer out there, IIS7 hardly even exists.
Michael's Techbox 
You’re kidding right? Your argument is against an update because /you/ have to support earlier versions.. And, this is not applicable to software in general, but unique to IIS7 how?
No, Yes, No and its not unique to IIS7. The article is about IIS7, and no I am not kidding, specifically in SOA applications IIS7’s advanced settings are generally not used industry wide. For smaller projects, or those where you have full control of you hosting environment (not installing at client sites), you may find yourself in the clear, able to take advantage of IIS7’s advanced features.
But since you asked a good question, compare IIS to Apache (either on Win or Linux) If you did need to update Apache you would not have to roll out a whole new server OS. You can simply update the web hosting software. However, if you wanted to upgrade from IIS6 to 7, the only way to do this would be to upgrade the underlining operating system. Although this is not a unique problem to IIS, it is a known Microsoft trend to bundle in features or limitations to operating systems, IIS7 is just one example of this. DX11 is another example, Browsers used to be tied to certain client OS’s but due to legal constrains MS are changing their browser policies.