Chef is awesome. We recently virtualized our entire production environment with the help of KVM + chef. Now installing a package or tweaking an install is a matter of updating some code.
We sure did! We had chef-client run continually throughout development so it continuously deployed as we pushed changes up.
For RailsRumble, in order to "complete" the competition, you have to tag a commit with "railsrumble" and make sure that was deployed. Once we had setup that tag, all we had to do was make a minor adjustment to our recipe and we knew that we'd have that tag deployed according to the rules.
This isn't the first time we've deployed with Chef which was great since we didn't have to fight with it at all.
Did you use Chef for deployments?