As a student in Missoula we went to Glacier a lot, and some of the best trips were in the Fall because of the beautiful colors, sparse visitors, and often a photogenic snowfall on the high peaks. October can have a long stretch of beautiful dry clear weather. We used to go climbing as late as Thanksgiving, and snowshoeing after that. It can be really good as long as you are self-contained.
There is an interesting photog link here: One year we climbed Heaven's Peak Ridge and while I climbed the actual peak my buddy took a 35 mm slide of lenticular clouds that fed him for many years. It was a bright orange sunset above jagged peaks. They captioned it "Montana, Land of Beginnings", and he sold thousands of prints throughout the 1980's and 1990's.
So this time of year can be favorable for photos; the best ones tend to be weather related: right as a front is moving in, or as the front is clearing off. Clear blue skies require a bit more creativity...
Fall always was my favorite time to go to Glacier!
Did you hear that the sea ice grew by 29% in 2013? Probably not. Big time denial going on amongst the warming crowd.