What's this welder worth?

[MercFan]

I'm looking for a good welder again. Found a nice MIG locally:

http://denver.craigslist.org/tls/2452454015.html

Guy wants $650 with bottle and regulator. A lot of money for sure, but from what I've seen locally it's not a terrible price for this unit - IF the unit is a good one I was as going to offer him $500.

Is this a good machine?!

Use: misc home projects, building some armor for my Land Cruiser (rock sliders, skid plate, maybe a winch mount). Most of my work should be in 1/16'' to about 1/4'' maybe a bit more but not much.