I really rely on my umbilicals. As much as they are a moving belay for me I also have come to rely on them to retain my tools while climbing leashless. On the occasions I do climb without umbilicals I am very careful to watch where my tools are all the time and that they are securely placed. And I don't worry about my partners kicking or bumping them off the climb. May be I should be more concerned all the time..
Good thinking Dane, I attach mine through cord anyway and your thoughts had crossed my mind too. On good ice, I don't use them, on mixed ground I am beginning to find umbilicals irritating with all the tangles around the rope, gear etc. Friends have had some success using a chest attachment point (8ft sling over shoulder, larks foot to harness, oh knot at sternum for attachment, oh knot under arm to take in slack).
My other worry with umbilicals is falling; fall on the wrong placement and the umbilical catapults your shiny sharp pride and joy towards your soft bits, ouch!
Don't on ice but on hard mixed and long (really don't want to lose an axe) routes I do. On mixed routes they are a completed pain in the a**se with tangles etc - spinner leashes would make no difference at all. Plenty of times been mid crux and unclipping umbilicals to untangle them! Might bump into you on the Ginat in a couple of weeks and we can compare umbilicals!