I did it myself, pretty easy.
When my new iMac came 4/16/10 I plugged it in and it asked me as part of initial set-up.
I had choices, one was via network which mine was.
(hardwired gigabit)
Since new iMac is on 2nd floor and "old" Mac in basement, easier than moving either one.
It moved 660GB of data, took like 6-8 hours over the network, did it at going to bed, done when woke up.