Now we're into tools that meet my criteria. The first is Task Coach.

Task Coach supports both folders and arbitrary task dependencies. Filters can be used to hide inactive tasks. It does pretty much everything I want.

However, the user interface is not so good. In order to define dependencies, you have to edit the task in a new window, select the "Prerequisites" tab, and then select the task or tasks that I want it to wait on. To be honest, this is too much work for what I expect to be a primary staple in my workflow.

Also, the UI is built in wxwidgets, which is better than Mono, but not by a lot. Nothing about it makes me want to use it.

On the plus side, it supports basically all desktop operating systems, and they have an app for Apple iOS. Plus they have SyncML syncing built in, so you should be able to sync with a variety of providers.

But I don't think that this is the one for me.