I found two problems so far in my trial version updated to the last version:
1) Deleting a project trigers a dialog saying that there are tasks inside even though there are none. This is not a blocking defect, while the second one is, at least for me.
2) After deleting some projects, it shows this error, and no restart helps. See the picture.
I like your app. It looks promising. There is however some way to go before it will be stable and therefore "buyable".