The Nico is one of my favorite bags! I find it super comfortable on the shoulder, and the strap doesn't dig in at all. The part of the strap that sits on your shoulder has a rolled/circular shape, so it doesn't dig in.
The leather is super amazing - although it does vary by color. I have the Nico in Currant and it is the softest leather I have ever touched (!!!!!) and also in Iznik Yellow. The yellow leather is still nice, but nowhere near as nice as the Currant. The lining is also different which may be of interest to you. The Currant lining is this marvelous vintage looking paisley with blues and purples, while the Iznik lining is the HH logo pattern. If you love linings, might be worth a call to HH before you pick a color!
I love big bags, and while I'm 5-7, I've seen this bag also look amazing on shorter women - there's a tPF'er out there named "momo" who posted pics of her Poppy Red Nico [in the "what bag are you wearing today" thread] and she is 5-4 and it looks incredible on her.
I love the Nico - it feels like I am carrying around a beautiful soft leather security blanket!