01. Getting information into Anki.
You've already got this covered pretty well. The ability to clip notes from around the web or add them via other methods is wonderful. Think of a tool like Evernote or Clip.to
02. Poor Quality Decks.
Let's face it, finding a good pre-made deck in Anki can be a challenge. You can easily solve this, simply offer your users a variety of high quality decks. The better the quality of the decks, the more value. It can take a REALLY long time to make a good deck, I'd gladly pay a modest fee for a well made deck that saves me hours of prep time.
03. Bad Design & UI.
I love Anki, but she isn't the prettiest girl in the room and she isn't always easy to get along with. A little bit of elegant design and thoughtful UI would go a looong way in boosting the perceived value of your product.
02. The best decks are always the ones you create, since they have personal value.
03. Ankidroid is the OSS android version and it's awesome. I bought the paid iOS app to support the author/service, but IMO it's really ugly and unusable (but then I think most iOS apps are unintuitive and crippled so take it with a grain of salt)