I've had mine for years and it is constantly out when I am cutting. I love it.
I don't understand BellaBoo's comment that it has to be on a table with 3 sides accessible. I used to just put it on a counter where only 1 side was accessible and I had no problem. Often at the quilt shows there is only 1 side available for the demonstrator to use and they do it just fine.
Of course, now I have a cutting center with all 4 sides open and love it that way.