Windows fan, but...
I seriously looked at Windows tablets, including the Surface, but there are several concerns I have which have kept me from purchasing one.
1. I have already invested money into apps for Android
2. Microsoft Office (emphasis on OneNote) would have been the main reason why I would have bought a Windows tablet, but Office 365 is now available on Android. And the Android 365 syncs perfectly via OneDrive with my desktop 365.
3. It's nice to have access to the same applications that run on PCs, but most applications that run on the desktop environment do not work well on small touchscreens. The ability to install desktop software isn't really an advantage at all...not yet at least. Try to use the PC version of Adobe Photoshop on a tablet.
4. A tablet for me must be a tablet and not a laptop hybrid. Keyboards are nice, but if I need a keyboard for my tablet then my tablet wasn't designed well enough. All the Windows tablets I've tried would need a keyboard for a majority of the desktop applications...then why not just buy an ultra thin laptop.
Don't get me wrong, I'm a huge Windows fan, but what I've seen up till now hasn't been enough to convince me to buy a Windows tablet. Currently I own a Samsung Tab S 10.5 LTE.