The litte girl I have is 3. If you've done any research you will find that whole language is pretty much the easiest way to teach DS kids to learn to read. So, this will be perfect. I do think the flashing helps. However, I wouldn't just use the program. I'd get the cards or print your own as well. We have found (thanks to advice from others on the list) that she enjoys the flash cards much more than the program. She will sit for longer periods of time when I do flashcards. My issue has been that I have children who really like this program and I just can't keep up with the flash card making. And I have a toddler who thinks they are great to crumple up and stuff in couch cushions.
So we have not been so good at using flash cards in addition to LR but she is still doing great. She has just gotten the hang of 1-1 correspondence so we recently started adding and subtracting. She can read about 200 words pretty accurately. The thing I noticed about her is that she is very reluctant to tell you what she knows. She will act like she has no clue when all the while she is sitting there with the answer. So, I don't test her a lot and we just trust the program is working. She has a huge vocabulary for a DS child. She knows all numbers 1-20 and can count forward and back. She has all colors down and most shapes. Here is a video of her playing piano with Soft Mozart - oh yes, we also use Litlle Musician with her.
http://www.youtube.com/v/SPLvpsILYfE&rel=1