I recieved an MMA 140 from Longevity Nearly a year ago. I had used this machine for a few demos and a few projects around the house. I really liked the size and capabilities of that lunchbox sized machine.
I recently went on a outage at a papermill with a good friend of mine and long term welding partner. I told him about the "Chinese" machine and he wanted to see it. So when the job was over he stopped on the way back to spend a little time here. We set the machine up and we burned about 10 or 15 rods with it and we went back and forth looking at each others welds. Never once did we fault the machine for one of our welds looking worse than the others.
Recently he stopped by to visit and I gave him the machine, he was grinnin pretty wide. I recently talked to him and he has used it and said it welds great. He only noted the difficulty in striking an arc on rusty metal (there is slighly lower OCV than on an industrial machine). This guy is pretty talented see the cannon he built from scratch and junkyard parts. http://www.weldinginspectionsvcs.com/cannon/Cannon.html .
Anyway, I think this machine is a great deal for the price. I purchased an LC416D so was able to give up the MMA 140 but cant deny that I miss the light weight and portablity of it compared to the whopping 28 lbs for the 416