I have 2 laptops, a Sony Vaio running Vista and a 13" Macbook, so I've gotten an opportunity to do my own first-hand comparisons. Both OSs are pretty stable, though Leopard has an annoying habit of locking up when the machine goes into screensaver lock or goes to sleep. The Vaio does this occasionally when I put it to sleep, but only about 1/3 as often. The driver availability issues for Vista have mostly been rectified, though Canon hasn't added 1Ds (the original one) support for Vista yet in their EOS Utility. The Mac version works, but with a retarded kludgy workaround requiring you to have the camera displaying the menu when you connect or the app will shut itself down. The Mac has major issues with the built-in Bluetooth hardware refusing to connect with headsets or dropping connections periodically that the Windows machine doesn't have. Overall both machines work pretty reliably; sufficiently so to be productive professional tools. Which one works best for a particular task depends on the individual quirks of the machine. But claiming one is significantly better than the other is nothing more than religious fanboyism.
I'd strongly recommend going with Vista now rather than waiting for the next version of Windows, which will probably be behind schedule, require updated versions of your applications, and need a service pack or two before it is ready for prime time.
