I don't really see a problem here. The only problem is people's understanding of what Windows 8 actually is.
Windows 8 isn't for desktop users. I wouldn't install it on my desktop, and you shouldn't install it on your desktop. We are at an awkward phase at the moment where the notion of a desktop user and a tablet user are two separate things. (Microsoft is the first company to make a move on this, and in 5 years time you'll realise how clever it was, this is why there is a lot of hate for W8 at the moment)
Windows 8 combines the tablet experience with a personal computer. Essentially its all the good bits of an iPad coupled with all the good bits of a desktop computer.
When you are carrying the device around, you use the metro interface and when you dock the device onto a keyboard, you use the Windows 7 interface.
So really, what's the problem? You can develop your metro apps for free, or develop a desktop version for free using the old visual studio (As windows 8 is backwards compatible).
Essentially all you are paying for is the privilege to have an app with a combined Metro/Desktop mode (I assume). And if you have an app worthy of that, then a $500 investment won't really be that big of a deal.
Its like Seppuku brought up Unity. There are a lot of core features missing from the Indi version of Unity (like shadows), and some might say that's a bit of a pain in the butt. However, you probably wouldn't use the Indi version of Unity to publish your games, nor would you immediately go out and buy the pro version.
You use the free tools they give you to create a polished application, then purchase the license/tool in order to get your product ready for launch.