I am looking for such application and I found Firebird, but can not use it, as it works only in Snow Leopard and my computer at work is Leopard and can not update to SL (work policy). Do you know about any similar app?
Not sure if it will do priorities but a popular GTD implementation on the Mac is OmniFocus. Will run on Leopard and Snow Leopard and the iPhone and iPad. It's "feature rich" so can take awhile to get used to. A simpler application is Things.