I still own a 1988 R100GS and love the character of BMW boxer twins. The pistons rise and fall in unison but fire on alternate cycles, so there's some vibration off of idle, but it gets very smooth as the revs increase. The heat isn't bad until the temperature gets well into the 90s. Having said that, the GL1800's side radiators keep heat off my legs better than any bike I've ever owned.