That one has become popular in the last few years. It is however expensive and somewhat limited in what it can do. The old fashioned C-frame dimpler has been around for a long time and has built a lot of sheet metal airplanes.

http://www.averytools.com/prodinfo.asp?number=1001

The DRDT-2 is one of those "nice to have but not need to have" tools, like a pneumatic rivet squeezer. They are nice if you have the money but if you are on a budget you can do just as good for a lot less money.