I can't tell you about the 6150 machine, since we don't have one. I can tell you that we have 2 Uni-bugs, a Stitch welder, a weaver, and several beam bugs. They all have been pretty durable in a fab shop environment and they don't get treated tenderly. We plasma cut, oxy cut, heat straighten, and FCAW weld with the Unibugs so I guess they get the most use. Just make sure the equipment doesn't get hot. I know that sounds like the obvious but everytime a machine goes down it's because someone put a torch ahead of the travel instead of behind it.
My biggest gripe is the cost of replacement parts. And the fact that people don't put parts back where others can find them (but that's not Bug-o's fault).
CHGuilford