OmniFocus is very flexible and fluid. It hides a lot of features in the interface gracefully, so they're there when you need them, but not drawing attention away from your work. Between views, projects, and tags, whatever your individual workflow for task planning, it can probably handle it. Review collected by and hosted on G2.com.

It's really pretty hard to use OF comfortably without at least some of the pro features, and the cost and feature gap between versions is significant. Omnigroup is moving toward a subscription model (who isn't?), but the price is steep—$100 a year for a single app. Otherwise, it's around $150 for both iOS and Mac, which you'll want. Review collected by and hosted on G2.com.