Follow up...
I got to use this new welder yesterday for most of the day. I'm surprised at how well this 110v wire feed welds even thick stuff. I've used up the rat's nest of loose wire that was on the roll, and I'm down to the good stuff. The wire is feeding nicely now.
I had one problem that I think I fixed. I posted it on my horse cart build thread, but I'll post it here too since it relates to this welder.
Near the end of the day the welder would sometimes run even when the trigger switch wasn't pressed. I limped it along to get to a good stopping place, and then I took the switch apart. I found frayed wires near the connectors for the switch. I taped them with electrical tape, and it seems to have fixed the problem. I haven't welded with it since, but I did cycle the switch a few times while I was feeding the wire after the fix. It was MUCH better.