Let's say I'm building something like an IDE, where I'm not targeting Xbox or phones. Is UWP appropriate for me? Should I aim to be on the Windows Store?
I don't know if it still holds for the cuddly "new" Microsoft... but tread carefully. Windows Store is curated and thus more restrictive than straight Win32 app development would be.
UWP is another story. With UWP, you have to deal with the mobile-like app lifecycle of getting randomly suspended and/or shut down. This is a hassle to deal with but understandable on a mobile device. For something as heavy, complex, and background-processing intensive as an IDE, it doesn't make sense to me.