I bought Reader Rabbit - my son won't even look at it. I was inspired to try these programs because my parents bought him Disney's Phonics Quest some time back and he loved it. He's always enjoyed Mickey Mouse stuff. I liked it because it was something he could do on his own (which I handle my younger one) and he was learning. At first he was just wildly guessing but after a while, when I peeped over his shoulder, I could see he actually knew the answers.
It's a fun way for him to learn phonics while playing a game. I wrote a review about it on my blog:
http://figur8.net/baby/2010/02/03/review-disneys-phonics-quest/