After some unsuccessful acceptance testing with Windows Vista we kept it away from our business environments, which saved us a lot of headaches. Many companies and institutions forget that the OS is just a vehicle towards the productivity goal. Aside from user comfort level, and possibly negative impact on productivity, you won’t get many changes by upgrading an old machine to a new OS. In fact, you will most likely cause worse performance and troubles on some older, slower and possibly incompatible hardware. Windows 7 is not as bad with hardware requirements as Vista was, but I still don’t see why you would want to put a new OS on an old PC. What does the job is beyond the OS, and it’s either software or browser based applications and it usually does the same thing regardless of the OS, so why bother?
Throughout my career I’ve gone through one forced company-wide OS upgrade that was a painful mammoth project because the decision was to upgrade ALL machines…. what a nightmare! The slowest and oldest 10% of them caused 90% of troubles. I’ve also seen and done several painless transitions where we chose to gradually phase in the new OS arriving preinstalled on newly purchased PCs and phase out the old OS with machines that get retired. No extra installations, no upgrades, no hassle. Easy money.
Windows XP SP3 is supported until some time in 2014, so except for the very specialized shops that need everybody on the same exact OS, I don’t see a valid reason to upgrade all business machines to the new desktop OS. After a satisfactory acceptance testing you can let the new hardware purchases with preinstalled OEM OS painlessly and gradually phase in the new OS for you.