Just got Zamberlain GTX on sale at REI. I won't buy boots from anywhere else in the future, I think, simply due to how hard it is to figure out if a boot is going to work for you.
My last set of boots were fine up to 5 miles. Past 5 miles, nothing I could do would prevent heel blistering. Cabela's wouldn't accept the return as they'd been visibly worn outside.
REI will let me return these things no matter what for a year. So far the Zamberlains are holding up great (please oh please let that continue....)