I agree with Gwen about the LOTW curriculum.
I have the K4 curriculum, too and I feel that it's kind of all over the place. Like, there's shape tracing and number magnets, but also vowel combinations?) I felt it was at both the beginning preschool end and the advanced kindergarten end (like with the vowel combinations and place values...but maybe my standards are 'off') but not a whole lot of in between? I bought it as part of a bundle & that's the only way I would go. Definitely spring for the extra $10 and get the bundle Gwen mentioned if you do get it.
There are a lot of different activities, but they are repetitive. I can't really see using it exclusively every day for any period of time. It's nice to be able to pick & choose from, but I don't find myself reaching for it often. Not really worth $20 to me. Plus, she really does offer a ton of freebies...and I think a good amount of them are in K4...you'd just have to download separately. Her writing practice worksheets are some of my favorites.
http://www.confessionsofahomeschooler.com/blog/2010/09/1-20-writing-practice.html
http://www.confessionsofahomeschooler.com/blog/2010/08/z-handwriting-worksheets.html