They are very nice and quite well built.  They definitely need a mat to keep items from slipping off.  The other problem is that when you have items on the table top and lift it to move it the legs start to fold in and when you put it down they do not spread back out.  Our living room where we use them is carpeted so pulling on the tray is not a good idea.  I suggest some sort of catch or pressure pt. when they are fully open ed.