I happen to be trying a Tab Pro 8.4 and also have an iPad Air (not an iPad mini, although I have used it), so I can compare the platforms side-by-side. My experiences:
- The display is about on par with that of an iPad... no, really. Samsung does have the DPI edge, but the differences in sharpness at typical viewing distances are slight. The colors and brightness are reasonably close on both, although I believe the Note Pro 8.4 might be more accurate than the mini (but not the Air).
- It's fast, but it hitches at times -- when you're swiping over to the Magazine UX, for example. Current-gen iPads are more consistently smooth.
- The interface scaling is generally fine, but you can tell that 2560x1600 isn't quite ideal. You'll occasionally run into menu items that are just a bit too small. And yes, the stereotypes of Android apps on tablets are generally true -- there's a noticeably larger volume of apps that aren't properly optimized. Android has its widgets, of course, although those aren't quite as useful on a tablet as on a phone. You don't need quick-glance info that much when you're sitting on the living room couch.
- Multi-window support is useful, but not quite as good as some would make it out to be. To me, it's a glass house: everything is great... until you have to do something that doesn't fit within those walls. It's a little too easy to run into a situation where Samsung's approach either isn't enough or falls apart (certain links may kick you out of multi-window mode). It suggests that Apple and Microsoft have better approaches: either have apps that were built from the ground-up for windowed use (Microsoft) or stay focused on a good single-app experience (Apple).
- Battery drain is definitely more noticeable. It's not hard to burn down the Tab Pro's charge than the iPad's. And yes, that involves heavy media use on both.
Both the iPad and the Tab Pro seem like worthwhile purchases to me, and the Tab Pro is definitely the most powerful small Android tablet on the market. It just isn't the home run that you'd think it would be at first blush.