Battery life isn't as good, but that could be Lollipop in general.
Actual problems:
Lag while pressing multitasking button (5-10 second delay, even with TalkBack disabled, and clearing cache and resetting to factory defaults)
Lag while pressing "review picture" from the camera (3-5 seconds to load the image, and then another 2-3 if I want to bring down the menu to share / edit, or even want to pass to the next photo by swiping).
These are ALL very well documented issues on XDA. If my Galaxy Tab Pro 8.4 can do multitasking faster and better than my Note 4, Samsung is doing something terribly wrong with their Note 4. I can open up multitasking faster on my Tab than on my Note 4.
Other than those issues, I think it runs perfectly, Very fast and fluid. But, sadly for me, I spend the majority of my time multitasking and taking pictures and reviewing them! haha. So, it's kind of big deal for me.