I bught a pair a couple of months ago - had heard of so many people buying them AFTER knackering their ankles and figured I'd rather not go that route! Personally, I didn't want to look like a stormtrooper and the protection they offer seems to be just about second to none.
  Like you, I had some misgivings about comfort when walking and spent some time wandering around in them before I bought. I had some Daytona roadstars which were like slippers (well I do have an ST after all!!! 

) the evo GTX are not as comfortable but perfectly ok for wandering around off the bike and really comfortable on the bike. After a while I hardly know I'm wearing them. 
 Apparently, it's not recommended to walk around in them too much as the sole is quite thin but Daytona do a re-sole service should it be necessary as well as replacement outers etc. I'm really pleased with them so far 
 Simon