Every gadget lover is, from time to time, tempted by the wiles of Sony’s industrial design. I myself succumbed to the then unnaturally thin profile of the VAIO F505 several years ago, and I enjoyed that machine for a while until it became so riddled with hardware problems that, eventually, I vowed never to buy another Sony computer again. So I was looking at Sony’s latest VAIO X505 laptop the other day, which bills itself as “featherweight” (1.84 lbs.) and looks about as thin as an issue of Newsweek (0.8 in.). It’s sexy, to be sure, but I’m reminded of the little calculation that I recommend for any prospective buyer of a Sony product: take the price tag and divide it by twelve to get the monthly cost of owning the product until it inevitably breaks.