L.M.
I got my daughter the Tag Junior when she was either 2 or 3 (forget which) and she used to love it. She would take it to daycare and "read" to the ladies when they were fussy. Then two years ago, we got her the Tag Reader. It works on the Junior books too, as well as other activities. She LOVES it. Of course, she has always loved reading and learning and being read to. She'll be 6 in two weeks and is in K. It definately helps keep her interested and allows her to read some on her own even if she doesn't know the words on her own. It keeps her engaged.
Her friend's mom got one for her friend last year who was in K and was struggling with reading and didn't really like reading. I haven't heard any complaints.
There are even more books for it now, including learning to read books (other than the story books). I am sure it would at least enhance what her teacher is doing in class.