I've worked in Denali as a guide for the last two summers and spent nearly every weekend backpacking.
Alcohol stoves work just fine—that's what I've used.
I've also used a down bag, which has worked fine for me. You can get stuck in days of 50F temps and rain, in which case nothing that gets wet will dry, so take care to keep things that have to be dry dry and make peace with the fact that when you're hiking, you'll be wet.
Of course, you can also hit long stretches of clear, sunny, dry weather, too.
I've never used gaiters in the summer up there, but I don't wear waterproof shoes, so I just give in to being wet from the knees down most of the time. If you've got the waterproof shoes and want to keep them from getting soaked from the dew that'll inevitably stream down your legs as you walk through willows, alders, dwarf birch, etc., gaiters might work, although I think rain pants (which you should definitely carry) would do just as well.