In this little post I explain why I think that you'll need to start developing for Windows 8 if you want to be part of the next big thing. Here are four good reasons, ordered by increasing importance.
It's easy
Whether you agree or not, developing software for Windows is easy. You get a top-notch IDE called Visual Studio, you are free to develop in either C++, C# or Javascript/HTML, there's good documentation, lots of frameworks, there's a great community behind .NET on both MSDN and StackOverflow and the support from Microsoft is excellent.
It's cross platform
Your Metro software will not only run on Windows 8 computers and laptops, it will also run on 'Windows Phone 8' phones and Windows 8 tablets. That's great right? No longer do you need to develop different software in completely different programming languages for your tablet or phone. How this is going to work out in practice remains to be seen, but it sounds very promising.
The Windows market share is huge
Nowadays it's a good idea to develop software for the iOS platform because it's the largest mobile OS. Windows Phone 7 on the other hand doesn't have a significant market share, making it a less important platform for developers. But that's all going to change. If you want a large platform with many users, start developing Windows 8 software. Here's why:
Between 85% and 90% of the computer users worldwide use Windows. That comes down to at least 400 million users. 400 Million. That's a lot of users. Let's say 50% of those users will migrate to a Windows 8 device in a time frame of 3 years. That's 200 Million users. Let's assume a lot of people will buy other hardware that easily connects with their computer and runs the same software. Do you see where this is going? Smells like Apple's strategy, but way larger in scale.
There's hardly any Windows 8 software
If you build something for Windows 8 now, whatever it is, you're probably the first to do so. The Windows 8 app market has, at the time of writing, only 99 apps, most of them not very useful. If your product hits the Windows 8 market first, well... You are the first. Profit right?
Summary
Windows 8 looks like a very promising operating system to me. The potential market is huge, it features a nice app market that's still empty leaving a lot of potential to you, and last but not least: it will run on all Windows 8 devices.