Take the Note 4 experience, remove the lag, add more speed, and that's the Note 5 in an nutshell. I'm pretty happy with this. It's even a tiny bit smaller!
HOWEVER, remember that some software changes have occurred, like the MultiWindow Sidebar being gone (MultiWindow is still there, just done differently) or different gestures for one-handed operation screen size and camera access. Also you lose IR blaster, SD Card support, and removable battery. If any of the latter is something you use a lot, you might want to reconsider (but since you're considering the iPhone, I'd say you don't care about these).
But if you, like me, are hooked on the S-Pen experience, only the Note line will give you that. And I've shown this phone to a lot of iFriends and every single one has come out impressed, saying it's the first Samsung phone they see that's lightning fast, lag-free enough to compare to their iPhones, with more features to actually make them jealous. And I agree with them.