Cool stuff! I completely agree that it would be awesome to add some sort of a reward system (like experience) in Anki to make it feel like you are achieving something, since it's hard to quantify actual gains made in language acquisition. Animations and sounds I think would go a long to achieving this goal. Maybe after every "easy" you get a special victory dance or something 
I think you should check out Progress Quest, they got the whole leveling/item/skill/story progression thing down pretty well. If you are going to do more stuff for this you should consider setting up a Google Code repository for it or something, so that people can easily contribute patches
Edit: I think it would also be interesting to set up a ladder where people can compete with each other for experience. This way you would always be motivated to do your reviews, otherwise you might just lose your rank!
I think you should check out Progress Quest, they got the whole leveling/item/skill/story progression thing down pretty well. If you are going to do more stuff for this you should consider setting up a Google Code repository for it or something, so that people can easily contribute patches
Edit: I think it would also be interesting to set up a ladder where people can compete with each other for experience. This way you would always be motivated to do your reviews, otherwise you might just lose your rank!
Edited: 2010-10-14, 2:48 pm