Well I'm in! No sweat at all (literally). Just a calm 8 mile shunt through London. Didn't annoy anyone :P It's a funny dynamic between cars and cyclists- find yourself continuously overtaking each other. Have to really have your wits about you too in slow moving traffic with cyclists filtering on both sides. Had a motorbike pull a dodgy move on me, but I spotted him in time. Providing you're eyes are open and you have a relaxed demeanor, it's fine.
Tell you what though, the cycle and bus lanes are a great thing for drivers and cyclists.
Good fun.