Outside of a number of things, like: Weird bugs (try typing in landscape mode in Mail... the text is cut off for me) Low volume from ear speaker for phone calls It may be weak and bend too easily (compare to Note 3) It's very big and awkward Here's the major problem: It's a tweener. What does that mean? It's such an odd size that it's effectively, in some ways, in between a full size tablet and a smartphone. No, it's not as big as a 7" tablet, a size typically used as the benchmark for tweeners. But it approaches tweener territory. And what does this really mean? It means that Apps need to be designed specifically for it. Right now, the lack of Apps is a huge issue for me. Everything is blown up and looks like crap. Facebook, banking Apps, everything. iOS does not do this well: it just blows everything up, including the text. It's pixelated and looks like garbage. This is in some ways even worse than Android, and I hate Android. This is fragmentation. Tim Cook and company should have done a lot more to prepare a better App showing out of the gate. And they should have done a deeper dive into iOS to deal with better scaling. I know to be patient as developers change their Apps and the 5S was a screen jump from previous iPhones, but there's the problem: It's a tweener, and it needs more customized design when it comes to Apps. The 5S was easy: it was just another row. The interfaces of Apps didn't really change at all. There was just a bit more vertical room for content. The 6 Plus is different because it's so fundamentally different as to be a huge leap in screen size both width and height wise. For example, Apple has introduced split screen in things like Mail, Reminders, etc. The problem is, it doesn't work very well because it's trying to do things that a large screen full size iPad does and it doesn't translate/work very well. And just blowing up the same interface from the smaller screened iPhones (e.g., 5S) doesn't translate either. I believe this is going to be a challenge and it's not clear what the results will be, or when the situation will improve dramatically. But my opinion is that the 6 Plus is a different category of device and developers simply cannot just make the same interface for a 5S/6 over to the Plus.