I have a Millermatic 200. It is an older model but I think any idiot can use the thing and get a nice weld out of it.
Having the 220 is def the way to go. Crazy that newer one (as some mentioned in this thread) can go 110 or 220.
I have used smaller 110 welders and its nothing like the big dog.
Since I have had the welder, I have become the go to garage for friends plows, trucks, toys. Cant believe I ever lived with out a welder.
Never will again. If your in the area and in a jam, look me up.
Have not tried aluminum yet. Friend has a gun I can borrow that plugs right in. Have a pontoon boat project this spring where I am going to give it a try.