Do you have a mobile app or a mobile-optimized interface? If so, you should mention it on the front page. I use Anki for studying vocabulary, and for reviewing I use the iPhone app exclusively. I only use the web interface for managing my lists. If you want to make a few bucks, you'll have no problem getting your users to cough up money for a mobile app, because of how handy it is to review in odd moments.
(I just checked Anki in the app store, and it's priced at $25 [1]. For the record, I paid less than that when I bought it, but I would have gladly paid $25.)
Also, make sure you test and advertise your support for non-ASCII characters and non-English dictionaries.
I designed a very similar spaced-repetition algorithm flashcard learning app for the Kindle (screenshots here: http://keminglabs.com/#/kindle/ ). It's in Amazon's review process at the moment, but if you have a Kindle and want to test it out I can get you a dev copy.
Tenjack---drop me a line if you want to chat about collaborating on some of this. We got our definitions from Wiktionary as well, but we're looking around for other resources.
(I just checked Anki in the app store, and it's priced at $25 [1]. For the record, I paid less than that when I bought it, but I would have gladly paid $25.)
Also, make sure you test and advertise your support for non-ASCII characters and non-English dictionaries.
[1] http://itunes.apple.com/us/app/ankisrs/id373493387?mt=8