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..
more here:
http://coldthistle.blogspot.com/2011/01 ... t-and.html