Early days of fooling with this app, but so far I’m loving it.
What’s really cool about it (and what brings it into the GTD realm) is that you can categorize your to do lists. This approaches the important context element of the GTD system.
So…for an artist you could, for example, have a category for gigs (or a specific gig), and group your to do items under it.
The designers of Do It have done a remarkable job in terms of options (iCal integration, alarms, customize-able skins, etc.). It really is a thing of beauty, and – b/c of the categories (“context” in GTD speak), it integrates into an existent system very well.