I found that my "ideal" phone size is about 4.75", in fact I switched from the Nexus 5 to the original Moto X because I felt the Nexus 5 was too large. Unfortunately, I'm old enough that I'm starting to really feel the benefit of having a larger screen. So I knew when I ordered, that I'd find the size of the 6P in my had as something less than ideal.
What has surprised me, I don't find the increased size any worse, for me, than the Nexus 5. Basically, they are both "too large" as opposed to my ideal. It is a little larger than I'd like in my pocket and I figured I'd not be able to fully use it one handed. Maybe because I was prepared for it being "too large", it really hasn't bothered me much. I do tend to keep it out of my pocket when I'm sitting but that is about the only concession I've made to its size. I've been very happy with the phone and quit noticing the size after the first week or so.
While I still feel, at least in terms of carrying and holding, that a sub-5" phone is my idea, I've found the larger screen is worth the small lack of ideal comfort.