I just purchased a pair of Montrail Lotus GTX boots that fit like they were made for me. I also tried on a pair of LaSportivas that felt heavier and definitely stiffer as they were new and the ones I bought had been hiked in a bit. Doing the MR in June myself and with the Montrails and Charlet Moser ***** Ice crampons I am all set. Definitely take your time to check fit for your foot, realize these are not running shoes, and you will be pleased with how they perform. Also, look into trekking poles for balance while crossing streams and such, then switch to an ice axe up higher.
Replacing the insoles with models you prefer further customizes the feel of the boot, and the choice of which sock you wear will make all the difference as well. I use a polypro liner and then a hiking sock on top of that. The Montrails are not leather, but Gore-Tex and nylon, but light, waterproof and an all around great feel. It takes some getting used to wearing more weight on your foot, but these boots also enable you to carry moderate to heavy loads more efficiently and with a level of confidence a flimsy hiking boot doesn't.