I also cooked a pork butt this weekend at 275 (+ or - 10 degrees) on my UDS. Plowboys Yardbird and seasoned salt were what I used for rubs - sparingly, at that. 10 pounder was probing just right in around 9 hours - coolered it for 2 hours, and it fell apart. Best one I've cooked yet.
Matt - 18.5" WSM; UDS; DigiQ DX2; Commercial Series Gasser; Maverick; Some Other Crap, Too!