Windows RT (aka Metro, aka Store Apps). It's a model based on WPF but not fully compliant - it took in lessons learned form Silverlight. Call it WPFlight.

That's the toolkit if you want Metro apps, dealing with MS's crappy store, etc. etc. If you want a traditional Windows application that just works, then WPF is fine. (And I think WPF has an option for non-blurry text rendering, whereas every Metro app seems to be blurry.)

Okay, yeah, so still XAML. I've only recently looked into Windows RT, my time was always spent in ASP.NET, so WPF/WinRT/Silverlight, it all seems like the same thing to me, but I do know a lot of Windows app developers that bitch up a storm about the diffs between WinRT XAML and what can be done in WPF :)

The truth is they are essentially the same. I just draw the distinction because porting apps between them isn't always automatic.