I have Both the Kel-Arc spot welder and the stitch welder. They are now made or are available from eastwood. It is about 155 for the set. I found mine used seperatly and paid about 30. The stich welders havent changed much in design, but the spot welders have changed some mainly in the orientation of the handle. The change is good or bad depending on preference, but i like the older models. On top of the design the older models were all metal and take more abuse around the shop. They are great for working in small areas and irreplaceable for working with thin metal. The spot welders are great because you dont have to acess both sides of the metal to use them.
As for the mig welder, they are much much easier to learn to use, and tend to make cleaner welds. I prefer them to do my autobody work, but still like the arc for other aplications in addition to being less expensive to use. I just got one of the gasless machines, but have not had a chance to give it a try. If i remember i will post on the sucess or lack of in the future