Still too new!
For serious application development your not going to get software written and approved in 90 days. Many developers waited until full release of the OS prior to investing into development.
Also the Modern UI metro type "app" seems to be predominantly non professional, games, and trinket apps that have little more than novelty value to desktop users. (Where most of the Windows 8 installations seem to be).
Microsoft seem to be offering good support, and pushing hard but its still early days for the more serious developers, and hopefully some full software enhanced for Windows 8 will start to become available over the next 6 to 12 months. At this stage it all seems like copies of IOS and android apps. (Not necessarily the better ones)
I hope the market doesn't go the way of IOS etc, being filled with the same apps with a different skins. How many "bubble pop" , "Jumping" or "hidden item" apps do you need?
