We have the square one from Leaps and Bounds (I think it might be made by Galt) and both of my older two jump on it every day. It provides a large enough jumping surface for my 4 year old to do the "seat drops" that he learned at gymnastics class. I agree with a PP that the folding feature is not really that useful and we have only used it when we need to move the trampoline into a room that has a small doorway. It was a Christmas gift last year and continues to be put to good use.
V, mom to
DS (2004)
DD#1 (2006)
DD#2 (2008)
DD#3 (2010) home from China 3/2012