I recently did a light and fast "done in a day" summit of Eldorado Peak in the North Cascades NP, it was amazing. It was a 15 hour day, with 7000 feet of elevation gain, and was just so beautiful! I highly reccomend it!
I got my pack weight down to 23 lbs, before adding any group gear like ropes and pickets. I noticed a few people on the climb were leaving gear like gaiters and rainwear (based on forecast) behind that used to be considered essential.
What do you carry for a "done in a day" glacier summit? Are there things you are leaving behind that you used to bring along?