I just got a pair of Schwalbe Marathon Pluses. It took me an hour to get one tire onto my rim. As I started to inflate the tube, the bead came out and the tube popped. The Conti 'City Rides' I was using prior to these Marathons were easy to get onto the rim and they fit well; no blow outs after 2500 miles.

The beads on the Marathon Plus series seem to run larger than 622 judging by the reports I've been reading for the past hour.