I haven't posted here for quite a while, but I still lurk
I made this change from e90 M3 to GT500 last November. 2010+ interiors on the Shelby's are good. Not as nice as the BMW, but not nearly as bad as people make it sound.
I have no regets on making the change. The supercharger whine, torque, and exhaust note are intoxicating. The Shelby draws a lot of positive attention. Here's a couple shot of mine with Ford racing handling kit installed.