I have the Millermatic 211 Autoset with the dual voltage setting and I absolutely love it. Haven't had to hook it up to 220v yet but I know when the time comes I have the machine for the job. Had a Millermatic 130 (or was it 135) before they came out with the 140/Autosets and although did not need it at the time I felt that if I ever had to fix or make something heavy duty I would've wished I had the 220v.
FWIW I've bought my last two Millers from this place...great prices and customer service.
http://store.cyberweld.com/mimigwe.html