I’ve gone back and forth between Things and The Hit List for a while, but I was never completely happy with either one of them.
I like THL’s user interface and flexibility to set up nested lists & folders, but I’m frustrated with the lack of an iPhone app, which I find essential.
I use Things just for their iPhone sync, but I’m frustrated with its inflexible structure and lack of folders or outlines with subtasks.
After trying the Mac app for a while, I finally took the plunge today and got both the Mac & iPhone versions of OmniFocus. Like The Hit List, OmniFocus allows complete flexibility to create outlines of subtasks and it goes even further by letting you promote a task to a project. iPhone sync is even better than Things, which can only sync over the local network. OmniFocus syncs via Mobile Me, so you don’t have to be near your computer to sync with it.
OmniFocus is more expensive than the other applications but it’s well worth the price if you want complete flexibility and iPhone support.