In reply to chaldakov:
Earlier this summer I spent a month walking in alps, up to 2,700m, a mixture of road, dirt tracks, trails and grassland. The routine was mostly one-three hour hill climbs almost every morning, anywhere where from 3-15 km walks in the afternoon and every third day or so walking between 20-30 km between towns. All this carrying a 23 kg rucksack but with walking poles.
From the outset I ignored boots and went straight with Merrell Moabs. But I soon abandoned them in favour of Teva Tera-Fi and Keen Owyhee sandals. Boots are a pain for me. They lack sponginess, hold water and sweat, are hot, heavy and don't provide any real ankle support - not enough to save you if you roll your foot. Also, the heels tend to be so high and the lack of tactile feedback from terrain leaves me far more unstable in them. The only advantage is the protection they provide from sticks, thorns, knocks against rocks and any cold (not an issue where I was).
Sandals on the other hand have some pretty obvious advantages. Your foot is free to expand, they are completely breathable, dry in an instant, are comfortable and flexible plus the keens had an enclosed toe and mostly covered exterior. The two pairs I had were almost fresh out of the box and gave me no discomfort or blisters. In fact I outpaced anyone I walked with and I'm pretty sure they were carrying less than the 23 kg I was.
The only downside was walking through fields where cut straw and sticks could work their way inside, as could small stones at times, and that your feet will get grimy (rather than wrinkled as they do in enclosed footwear). But these were irritants. Walking through streams, dew covered grass or wet ground was no longer dooming my feet to several hours of soaking, my knees and ankles thanked me for it and walking was simply far more pleasant.
My feeling is boots, and possibly even trail shoes, are largely over-spec or a hindrance for anything other than really rough terrain or extreme cold/weather.
Post edited at 14:46