Not only am I a multi system user, but the systems I use are constantly changing (more or less). Right now I shoot m4/3, 4/3 DLSRs, Canon APS-C DSLRs, Pentax APS-C DSLRs and my trusty Fujifilm X10.
A few weeks ago Pentax wasn't in that list but Nikon was. A few months prior to that Nikon...