I don't know how feasible this is (or in fact whether there'd be any interest in it beyond my own), but it would be great if attached to each word there was a small blank pad to add your own notes from a lesson (e.g. grammar structures, linked words, relevant points on how to use, maybe even a few example sentences that you want to jot in quickly rather than add to the example sentences section).
I currently tend to do this in the mnemonic section, but it's not so convenient when I want to actually have a mnemonic too (esp when I switch to the iPhone app).
Just a thought.