I would love the ability to label my guides. In fact maybe a hole overhaul to the guide system. In After Effects and Premiere you can add Composition Markers, give them comments and adjust their perimeters. It would be great if you could do that for guides.
On the rulers will show a marker. Double clicking the marker will bring up the Guide Controls. or when you select 'New Guide' from the drop down menu, Guide Controls takes place of the window that currently gets displayed.
I would love this across all programs: Photoshop, After Effects, and the like, not just Illustrator.