Well, UI isn't very testable and it's what the users actually see. Under the hood improvements are likely to go unnoticed.

Even with the best of UI's, a workflow riddled with spikes and potholes can halt user adoption (I learned this from FreeCAD after days of visual and keybind customations, only to find out I can only pad one singular profile at a time). 

Ignite also showed me that a good UI can nullify my desire for an update (I don't think it's had one since 2013) because it looks and feels modern and made years before its time. I've heard a similar thing said for the Windows Phone and Zune interfaces, and I'd agree even though I never got around to trying either.

I'd also like to mention that my prefered interface styles seem to be menus for games, consoles and media centers, so yeah I'm 100% adding button click and animation sounds to this installer (and the programs its for (+ a mute option)). 

I'd also like to take Microsoft's animation ideas and actually get it into some end-use software, and maybe squeeze in a bit of the PS Vita's Welcome Park experience in too.