I love that shake too. I have tassles on my brake/clutch lever and at idle, they bounce like crazy, but once I rev it up a bit, they get deathly still.
As for changes, the 2010 got helical cut 5th gear so it doesn't whine (though I like the 2009 whine as it tells me what gear it is in). For 2011, I don't think there were any real changes to the Road King, though the Road King Classic got the 103" motor standard, as well as ABS. Cruise was already standard on the RKC.
For some reason, the 103" isn't available from the factory on the RK standard.
Either way, you'll love it. I have 11k on my 2009 RKC and love every mile of it.