[imdsm]

If I can just add a slightly less critical point to the above — yes, the $5 price turned me off, but I think it's a great concept. As I read this, I had physical revision cards in front of me, filling them up with formula prior to joining a lecture, so I could use them for reference.

Would I use this for book marking formulae and research? Potentially. But would I pay for it? Sadly not.

It's a great idea, but there have to be two things to make this successful I think: a useful concept, and a tool valuable enough to be worth money.

Good luck, and don't give up!