Not too long ago I ran a poll asking developers whether they already started developing applications for Windows 8. There were a total of 127 votes cast, with a surprising end result. But let's start from the very beginning.
Answered 'Yes, actively.'
Total votes: 11% (14)
Answered 'Yes, recently started.'
Total votes: 14% (18)
These are the developers who are enthusiastic about the new platform but until recently didn't feel the need to build Metro applications, either because of lack of time or resources, or they were simply not sure where the whole Metro-based enthusiasm is going to go. Also, this might include beginner developers. Despite the common misconception, there are already plenty of resources to get you started with Windows 8 development for developers from all levels.
Answered 'No, not enough documentation.'
Total votes: 6% (8)
I can see why developers who voted for this option felt that there is not enough documentation available. The current MSDN coverage of the Windows 8 APIs is pretty limited, as in - it requires previous development experience with the platform in most cases. In defense of the current situation, I must say that since it is a Developer Preview, the APIs are not yet locked and are subject to change. So is the documentation. It would make no sense to write extensive chunks of MSDN snippets when all of those will have to be re-done in a couple of months. On a side note, for the most common capabilities introduced in Windows 8 there are plenty of unofficial blog posts and articles that go in depth about some development aspects. Not the perfect solution for some developers, but that's what happens before the release of a large new product.
Answered 'No, don't like the limitations.'
Total votes: 18% (23)
Metro apps do not behave in the same way standard Windows applications do. In a lot of situations, Metro applications are a lot more restrictive and controlling as to the data and hardware the application can access. If you've developed for Windows Phone, or any mobile platform for that reason, you know that each application runs in a sandbox limited by some declared or system-assigned capabilities. Later on, the user can decide whether he wants to run the application by reviewing the elements of the system the application accesses. Metro applications have no access whatsoever to system files and only allow access to hardware that was specifically allowed by the user. There are also limitations connected to application distribution and integration.
REMEMBER: Metro applications are not the replacement for desktop applications. The Metro UI in its current state will be mostly used in a mobile environment (read: tablet), where the limitations described are already widely adopted on the majority of platforms.
Answered 'No, other reasons.'
Total votes: 51% (64)
These are unknown, but might include: lack of support for certain libraries and programming languages, no cross-platform compatibility and currently existing bugs and issues in the development environment.