Personally, Windows 7 is my last OS from Microsoft.
That said, no one should ever consider using a Microsoft operating system until they get service pack one out the door.
Remember when Vista was released and everyone said it was the best? We all know where that went.
Remember when Windows 7 came out and it was the best? It sucked until SP1 was released. Heck they just fixed a memory leak in the desktop shell, which has been an issue since the OS was released!
Windows 8 was the first Microsoft OS which was only lauded as the next best thing for a few weeks. Proving there is hope.
Now with Windows 10, we are back to hearing about how it is the best thing since sliced bread and it is still in development.
While we have to make sure the game runs on Windows 10, we will be installing it and testing with it, after it becomes a real product. Right now Windows 10 is a noisy blip on the radar. Once it is really released, then we will be looking at it.
Right now the most stable and best released OS from Microsoft is Windows 7 64 bit.