The marin is kept for sentimental reasons...its been mine since new...doesnt really get used anymore. The Roberts is too pretty to use all that often...very much a summer bike.
Most my riding over the past few years has been done on the 2005 KHS and then the 2008 Epic. The 2010 t'inbred is to probably going to take the place of the KHS.
(actually thats all a lie, my RC100 has seen more use over the winter than any of my mountain bikes, and the bike which has seen the most use over the last year is my Mtrax racer that I use for commuting, the KHS & Epic only really come out to play on biking weekends...once a month or so)