Not the biggest fan of mono in general, but I think the 2011 mono mix of "Cabin-Essence" sounds pretty cool, especially with Mike's pitched-shifted vocals during the "Grand Coulee Dam" section.
Pitch-shifted? I'm not remembering this...
Compare the stereo 20/20 version with the mono Smile Sessions version, you'll notice that Mike's line (over and over...) is pitch shifted by about 2% or so. It sounds more in tune with the rest of the track IMO.