I have used a Lincoln 275 (I think?) MIG for about 6 or 8 years and if I keep good tips and gas shielding nozzles on it, I can't complain about it too much.
I use it mainly for welding the rolldoor latches that I sell, and I usually make up four or five batches a year so it collects quite a bit of dust between uses. I find that for doing repairs to macinery, the old Lincoln stick machine can't be beat. Unless, of course you are doing light stuff.
But a MIG does not like welding dirty or rusty naterial. NO, no, no.
This welder cost about $1600 new but does a lot of heavy work for me. I have a jig that I put the parts in for welding and I am doing around 125 parts per hour. The gun is suspended above the jig and it welds for 7 seconds (manually triggered) and is off for about 12-14 seconds while I reset the jig.
I run this thing at that speed for about 2-3 hours at a time (between looong coffee breaks!)and have good results with it AS LONG AS THE TIP AND NOZZLE ARE GOOD. If they are not, the thing will drive me crazy with bad welds and wasted parts. So that's a high duty cycle, especially when you consider that the wire speed and voltage are set almost at the top. It's almost like spray welding.
I also switchd to a 300 amp gun and found it was a lot steadier feed than the original lighter gun that came with the welder.
Having said all that, most guys around here use Millers.