I've flown in 767s five times that I can remember. AA on the DFW-LGW return route in '87, SAS on the CPG-ORD route in 1996, and Aeroflot on the ORD-SVO return route in 1999.
AA was good...seemed pretty roomy, nice layout in the 767-200. I enjoyed that flight, especially the international service.
SAS was not good at all. This was a 767-300 ER, and though it had the 2-3-2 layout, the seats were close together and the plane was PACKED. Very claustrophobic feeling. I didn't enjoy it, and I was in the middle row on the aisle. Though footrests for every passenger are a nice touch. Aeroflot's 767-300ER service was the best I've experienced; I sat just behind the third exit/emergency door, and had all the legroom I could handle, and the seats were wide and comfortable, even in coach.
Overall, I love the plane, and I can see why so many airlines have them. I'd rate it 8.5 in terms of overall comfort, though this totally depends on the airline and layout used.