i have the 24-70 2.8 EX, and as far as i know it's the older version of this lens.
the af/mf switch is a bit of a pain tbh, you have to flick a switch on the barrel and then move the focusing ring backwards or forwards to engage/disengage the af. i rarely manually focus this lens though (prefering fast primes for that)
what sort of money is the EX going for?