I´m using Weekplan for a couple of weeks now and find it VERY useful. It has lots of really useful and well thought out features (like that tasks which are not completed at the due date automatically go to the next day). Weekplan is one of the apps here on Appsumo which don´t stand out as much as others do but delivers great value. That said, I have to admit, that it still needs improvement on different topics. The learning curve is a little steep, some of the articles in the documentation (which is helpful) are outdated and not everything is clear at a first glance (e.g. I still don´t know what the difference is between the parking lot and the backlog).

Conclusion: Buy it, try it and you (most probably) will use it every day!