I've been using http://SergiuRecommends.com/BizPad for my task/project management. It's an up-and-coming tool (Web-based), and I found its simplicity yet power quite remarkable ... pretty much the same characteristics as Klok. In a sense, BizPad and Klok are complementary: the former is mainly about planning (future), the latter is mainly about tracking (present/past). It would be a natural integration, and a powerful one ... if designed carefully and done well.
I happen to know the people behind BizPad, so I can introduce you two. Take a look at http://SergiuRecommends.com/BizPad (there is a 30-day free trial, enough to get one to experience it well), and let me know.
Questions? Email or phone me.
Thank you for your consideration.