I'm a little disappointed in mine so far. It's only at 646 miles, so I realize it should go up some, but as of now my average is 15.2 MPG with about 70% city driving.
I'm sure this is also partly due to being a winter fuel mixture, and my daily commute is about 3 miles round-trip.
Aside from my current fuel mileage, I have absolutely no complaints about getting the V6. I don't tow and only haul light loads, so the extra $$ for the V8 isn't worth it for me. I've driven several of the previous generation GM trucks with 4.3, 4.8, and 5.3 motors, and my butt dyno can't tell a difference between the 4.3 V6 in my 2014 regular cab short bod and the 5.3 V8 in my dad's 2002 extended cab.