Indeed, OmniFocus is the best GTD implementation I’ve ever used. Nonetheless, I do not yet recommend it for general use, because, in my opinion, problems with the interface would actually prevent most users from freely accessing and manipulating their data.
Maybe it’s because I’ve never read anything about the official Getting Things Done system and simply tried using OmniFocus to (lowercase) get things done, but I found it to be difficult to understand. Neuburg’s complaints help me put my finger on what I don’t like about it. Don’t miss his screencast addenda to the article, regarding the UI details of the app. In fact, the screencasts might even be better than the article.