My Take
It's a bit expensive though, about $219 for reading a-z and raz-kids alone without writing a-z however, I found a deal on eBay.
How I Use It
I was looking for some great tool for my homeschooling kids last year and came to know about raz-kids. It's a great web application for developing good reading habits. I found my kids were using it by themselves without any assistance and it keep continue moving them up for reading next book.