WHen I've used rewards for reading, when DS needed something to get him past seeing so many words on the page, his reward was to go to the bookstore and pick out a book either for him to read or for us to read to him.
When we were in the doldrums finishing up his math curriculum for the year (I'm not confidant in the school's math curriculum), he got to pick something to celebrate finishing. We discussed the contribution each family member made to his goal of loving, learning, and finishing math (Dh earns money to buy the curriculum, I go over it w/ him, brother has to play quietly while DS does it) so he picks things for the whole family to enjoy such as dinner at a restaurant of his choosing, ice cream, remote controlled helicopter we all enjoy flying etc.
So far I've not seen any negative effects from this. I'm definitely in the intrinsic motivation is better than external motivation camp. The school encouraged me to try an external motivators for DS to get his homework done...it worked somewhat but external motivators have never worked all that well for him and I have trouble remembering to do it and following through.
