I've been in hiatus from using EiffelStudio on the Mac for a while because since the upgrade to Leopard, EiffelStudio exhibited some strange behavior related to expose actions. As a result elements of the UI, that are custom drawn, went missing. I was left unable to see set breakpoints and the docked tool tabs.
Paul suggested a very nice tip with the wild card completion (new feature of 5.7). I'd like to show that there is an even older feature that is pretty much unknown to many users. It is the routine argument filling facility.