I used the TF for over a year (so I could accumulate more DVD's) and just upgraded to Cathe's step. Mostly the TF was fine, but I totally agree with Kathryn that the surface is different. Cathe's step gives a lot more, so when I do high impact, my knees aren't taking a beating, like they did with the TF. I can't even say that I noticed a problem while using the TF, but now that I have switched, my knees are much happier.