I bought the 2015 250S with SM200 spool gun. MIG is excellent with great control arc control. TIG works well, but I'm with TheGary on wanting AC TIG option, with the inverter base, I'd think this wouldn't but that much more to ask for this unit. The stick side has great arc, especially when fine tuning with the arc force. I love the infinite control of all parameters.
Now to the spool gun. I actually wanted to do a quick repair outside, but didn't want to use stick, so I threw a roll of flux core in my SM200. It would be nice to have some type of documentation with the spool gun, so I had to tinker with it to figure it out. Once I got it figured out, dialing in wire speed was so nice since it's at your finger tips on the gun. I thought it might be a little awkward to use with the weight of the spool, but found it to be balanced well. After some time with it, I can see using the spool gun a lot more. I've got a longer work clamp cable now, so I can leave the welder where it is, put some solid wire in and use with gas, and work on stuff across the shop with easy set up.
When working on thinner stock, the 120v option is great, and makes for better flexibility. Most of the stock I'll be welding will be at most 3/8", so I don't foresee running into any duty cycle problems. Overall I am more than pleased with the PowerMTS 250S and SM200MTS spool gun.