I have not seen that many for sale and for me it was the best thing I ever did to my 2011 Ultra Classic Ltd... The fuel mileage is about the same IF you keep it under 3000 rpms...
But if your a modified Yamaha Raider trying to show off - look out. After riding one on one, I am sure he is looking to trade it in...even with all the one wheel riding he was doing trying to keep up!!!
HD-Ben
LOL, finally. Currently in the process of selling my 2009 Raider after just enjoying the hell out of my Ultra. Enjoy the Ultra so much that she's getting a stable mate (2007 Softail Custom). Not sure which one will get a 120R (or S&S 124) first to take care of business but it'll be fun either way.