I leave my laptop in the office whenever I can because it's a boat anchor. When I have to transport it, I use REI's Novara Commuter Pannier with an REI laptop sleeve. I haven't had any problems with this setup. I used to carry it loose in an old Bike Warehouse pannier, but one day the pannier bounced off the rack and the laptop took the full force of the fall, but it only cracked the trim around the vent.