When dealing with segmentations, and particularly large segmentations, Marketo can sometimes take up to 24 hours to approve them.
The problem is there's no real way of knowing how long the Approval process will take.
So I think it would be extremely useful if there was a progress tracker situated on the main menu of the segmentation (next to Status) which could provide an estimated Approval time.
Taking the idea one step further and have an option to select to be notified once the segmentation is Approved.