Agreed on the Miller Econo TIG. We had one where I used to work mounted on a cart for portable spot jobs and the thing worked great. Never did use it for aluminum because we had higher amp and duty cycle machines for that. I could see where the 20% duty cycle and 160 amps on the high end could restrict to the thinner aluminum. For "most" jobs or the backyard hobbyist, the Econo should be fine.
