Ive got 2x 580exII and 1x 580ex... the 580ex has a nice switch for choosing master/slave mode, the 580exII is a button function, i was in the same boat as you, and was thinking of getting a 430ex off Kerso, when i got the price for the 580exII off him, i was that shocked i ordered 2.
I paid £225 each on them and im getting £40 cashback on each off Canon, making the 580exII effectively £185... which is about the price a 430EX is at most places. Please dont quote me on the price, check with Ian directly as i did order a few bits so may have recieved a discount.