nice choice of boot. you'll get used to them quite quickly, the main part being getting used to something around your ankle and even weirder at first, the comparative rigidity. although they're comfy from the box, take every opportunity to wear them so that you "break" them into your feet and stride so that they become super comfy.
take longish walks as unless you're used to being on your feet for hours at a time you'll get very "tired and achey" feet until you get used to it - it will pass.
this will also enable you to experiment as to wearing a liner sock - some people prefer them, some don't. i wear a thin coolmax sock under my usual ones. the double layer relieves some of the rubbing of the outer sock as it rubs against the inner rather than your skin. haven't had a blister yet (touch wood) - horses for courses really. they dry really quickly and i carry a spare pair should i need to change them to let them dry out a bit.
get used to the fact that you ARE going to get hot feet. the less you think about it the less a problem it is.
boots are heavier than sandals (sorry bout the bleedin' obvious) - you'll soon get used to them again. you'll appreciate the support, especially downhill, and the grip.
ooh - i'm waffling again..........