i use an Arkel briefcase, but their sleeve didn't fit my new Macbook pro (old bag i've used for about 10 years), so i just stuffed the laptop into a third-party neoprene sleeve, shoved it into the bag, and off i went. works like a charm. plus, i can throw it into a backpack, into a smaller pannier, or anything else--not limited to only one bag for carrying it.

while the arkel design is kind of nice, if i crashed--and i mean at speed but not a collision--and the bike fell on the laptop-bag side, it'd probably be smooshed no matter what. to this end, even a neoprene sleeve is just there to make sure the mashed laptop is all mashed up inside a convenient bag.

so what to do? ride carefully, make frequent back-ups, and know where to find a spare machine in case yours is dead. and if you're laptop is that pricey, well, no bag built will sufficiently protect it, on a bike, in a car, or even from one room to another.