My best would be the Meindl Island pros, fantastic things in every way, so high I never felt the need for gaiters and as comfy as slippers, unfortunatly my feet decided to have one last growth spurt at 20 (well could have been the start of middle age spread?) and they became too small, grrr.
Replaced with Meindl Dovre extrems, very comfy with the right sock combo, they've done quite some mileage over the past 10 years or so in some pretty grim places and I THINK THEY ARE STILL BREAKING IN! If they last another 10 years then they'll have been worth the purchase price over the rest of the range and go to top spot. Always get remarks about them which is also nice.
Worst boots is an easy one, Berghaus Kangs, 3 season goretex fabric boots, stupid seam right on the heel, blisters and hole within the blink of an eye, fine in the shop, but once I had some weight on my back, sheesh. No support in the upper (same as the storm alluded to above but a ring higher) but a really stiff sole unit. Only once in the two years I suffered with those boots did they feel they were in the right place, doing some hard scrambling up the side of the cavall de bernat ridge in Majorca in 40 deg c, brutal.
Special mention to my Scarpa Vegas, for keeping my feet toasty in the Alps during my 'Ice climbing' years, when all my mates were 'manning it out' in the then new fangled super stiff leather ice climbing boots like sportivas and Salomons, how I laughed while they danced away the frost bite...
Still got them somewhere just in case we get another ice age
