Im a big fan of the global queue. Its good to have an overview over what you have queued and its a pretty fast way to cancel techs or Units that are in the queue (with shift + click).
My only problem is that you are only one miscklick away from cancelling your age up which can cost you the game and has cost me some games. The biggest problem is for me when i cancel units right before hitting the next age to have the res for the upgrades and then cancel the age up 11.
My suggestion would be similar to the save delete feature that it asks you to confirm that you want to cancel it, since its also pretty rare that you really want to cancel it in the global queue.
Another way would be to make it so that you can cancel age ups only in the building, but there are different solutions to this im sure.