I'm coming from a Lumia 920 on Windows. I've found the app gap to be a much smaller issue than the media makes it out to be. I love the phone, though. The screen is great. I don't mind the size most of the time. I have large pockets and it fits pretty well. The only time it bothers me is when tying my shoes.
I like the s pen a lot. It really gives the note something no other phone has. It's not something I can't live without but is extremely useful.
The camera is great. Very fast. Lots of detail. Great shot to shot times. Cameras are very important to me and the notes camera is the best I've used.
I have a few dissapointments. Some are a lack of customizing on my part (keyboard, lock screen, launcher). I don't like how much space there is between icons. There is some slowdown here and there. The keyboard isn't as good as the stock WP keyboard. The lock screen and s view window are limited in functionality. I'm sure most of these issues can be remedied with a new launcher, lock screen, and keyboard.
My biggest complaints come from car integration and Xbox music functionality. WP was significantly better with both. I can't do half of the things with the phone in the car that I could do with WP. Xbox music has limited functionality. I understand the issues with Xbox music. I'll either work around them or switch to another service. The car functionality is a bigger issue and I haven't been able to find a working solution yet.
If it weren't for the camera, multitasking, and pen I'd switch back to WP. I'm still undecided at this time.