I don't see it as a tool to teach you "creative skills", not at all! I see as a good brainstorming tool. A good, simple one. The main advantage to real meetings brainstorming sessions is that this is asynchronous, your team doesn't have to be all together at the same time. You may just say "let's brainstorm this through the next 3 days, and friday we decide what to do". And I liked the 2 nudges I got very much! And I like that is not that easy to skip.
But, as a web app alone, with very poor social resources, it lost all its appeal. Something that I think would make it great is to allow all communication to be made through email (just as Basecamp and Asana do). But if everything is via email, then it may be very powerfull. But you have to create a great UX with added value, because one can simply create a email, copy 3 teammates and start a brainstorming thread. How to introduce the nudges, a good organization of topics and ideas, an easy to upvote good ideas maybe, etc; that would be hard to do through this email communication.
Well, I think the concept is great, I hope you can make a good product out of it.
