For those of us who don't have easy access to 240V, a 120V has to be good enough.  I went with the idea that, when I do have 240V available I will spend money for a real nice welder, for now I wanted a 120 that would get er done for a decent price.  I am using a Clarke 135 machine.  It isn't a Miller, but it is far better than the HF super cheapo I had before.  The key really is that prepping your joints becomes more critical because the machine doesn't have the balls to get through some of the thicker stuff.  I haven't had any problems with weld strength yet...they are all holding strong.