Take what I'm about to say with a grain of salt since most trucks with problems are 2012-2013 from what I've seen. But I have had experiences with 3 FFV Tundras personally. 2010 Double cab short box 4x4 (totaled @ 55,000 miles), my current 2011 Double cab short box 4x4 (27,700 miles on the clock), and currently a 2014 Double cab short box 4x4 (3,200 miles on the clock) and none of my trucks have had issues.
When all 3 of these trucks were stock, I got 18-21 MPGs doing pure highway trips. Now that both my 2011 and the 2014 both sit on 35s with lift kits they get roughly ~15 MPGs now if I'm lucky. When towing is about 7-10 MPGs, so it's not amazing.
I will say, my dealership said they were aware of the issue when we purchased the 2014 FFV. But they also said the reflash had solved all the issues and hadn't had anymore complaints from those owners that got the reflash.
I live in Missouri and I fill up my 5.7 FFV Tundra with either regular 87 or 91 octane gas, and like I said I haven't had a single issue that a lot of people complain about.
I do feel sorry for those experiencing the issue, and I know there is a problem. But I think labeling all the FFVs as complete junk is ludicrous.