Your comments

Sergey, thanks for your answer. But unfortunately I don't really understand how tags will help my users to express different grades of positive/negative interest.

And I'm not using the service as a todo list, I'm transferring the existing ideas and bugs from my PHPBB forums: http://cintanotes.com/forum/viewforum.php?f=4

Thanks a lot for your generous offer of the Power plan! My software is free now, but there's also a commercial version planned. Does your offer still hold under such circumstances? As I'm working on the program alone and don't see yet any income from it, I can't really afford to pay $15 per month.

P.S. Eще хотел сказать - вы молодцы, здорово видеть как наши программисты делают хорошие сервисы ;)
I would need tab "Tips" for users giving advices to each other on how better use the product. It also won't hurt to have tab "Other" or "General" for issues not falling into any category.