Greg, 

Thanks for the great summary of GNP. It has been one of my favorite destinations also. I have backpacked, car camped, stayed in park lodges and last couple of years Scamped. I've enjoyed all of the visits.

 Another good hike is from Logan Pass to Granite Chalet, via the garden wall. The trail ends up at the loop where you can catch a ride (shuttle in season or hitch hike) back to Logan pass. Early October is my favorite time to go because of fewer people and you can drive to and park at Logan Pass at least until the pass closes. The closure date is determined by weather and varies from year to year.  Apgar campground (west side) is still open then although water is shut off and outhouses are provided. Many Glacier cg on the east side is open without services until late October. Many Glacier is the trailhead for many spectacular hikes. St Mary's cg (east side) is also open later in the fall season.

I'm not sure there is a bad time to go to Glacier. In the fall, prepare for any weather conditions including snow. Come to think of it, I've been snowed on there in the summer.

wayne