Tim at Hawk Wings beat me to the punch as I was going to post about this. Recently, there was an excellent write up on the Yojimbo mailing list by user Robert Foxworthington on implementing a GTD system in Yojimbo using a combination of collections and tags. Great example of how, with a little outside the box thinking, you can implement a GTD system using almost any tool. The reason: It is not about the tool it is about having a system that you trust.