I do it and love it!! Three of my sisters do it and my sister's SIL is on the homepage (the pic of the "backfat" lol) I think it's awesome and have given away all my other exercise tapes because I really feel like this is all I need. I'm t-tapping and walking/running on the treadmill and planning for great results.
I'm sure you've looked at the website, but the forums there are a wealth of information. To read the testimonials of those it's worked for and especially those that have had had knee or back injuries and have been rehabilitated. I'm certainly no pro yet, but if have any questions that I can't answer I could probably find the answer out from someone.