I have (in the family) a Lincoln 250 Round top, an Oxyacetylene setup (and a Hen-rob now), one of the little Lincoln Flux core Costco specials, and a Daytona Mig 181C. I like the Daytona Best for General use. It's biggest problem is getting the wire feed adjusted down, but it was a floor demo model and I think the local dealer may have replaced the rheostat for that with the wrong one.
I would buy a mig for anything you listed with the exception of aluminum. I have done aluminum with the Daytona and my best welds are UGLY. I had the use of a tig on one job and it was fairly easy to get a decent looking weld with it. The other gripe I have is if you weld aluminum with a mig you have to get a plastic liner for your mig gun / lead. That's not that big a deal but as the Daytona is a normal mig (pushes the wire through the lead) you are limited to about a 6 foot lead. That may sound like a lot, but it's a pretty short 'leash.' Even at that the soft aluminum wire will "birds nest" in the drive at the slightest excuse.
Don't misunderstand I know there is a boat shop around here somewhere building aluminum skiffs with a mig welder and their welds look fine. I just don't know what they are using.
