I'm a huge fan of spaced repetition and a regular Anki user. I think the value proposition is a little too vague here. It seems like your target market is people that don't already know about or use spaced repetition. In order to win them over, I think you need a more specific reason to use the product.
I saw another YC company recently that is using spaced repetition as a means for corporate training. I'm not saying it's the best or correct market, but that strategy seems plausible to me.
Good luck!