I have one, got it through my dealer (who probably ordered it online and charged me extra!) and I couldn't do without it. That said, if I had to do it over again, I'd go for something bigger...like a dining room table. LOL Extension tables are fairly easy to make out of wood.
Fabricluvr made one
http://www.quiltingboard.com/t-11611-1.htm
or you can go the USPS box route like katier825 did
http://www.quiltingboard.com/t-21180-1.htm