"Windows 7 is set apart from the previous batch of Microsoft OS upgrades by many factors. First, it's designed to be compatible with Vista hardware and drivers. This means that, in theory at least, a laptop capable of running Vista comfortably should run Windows 7 just as happily.
Second, the public beta was made widely available and lasts up to six months. This gives the testers a long period to help iron out teething issues before the OS's release, instead of users having to wait for important fixes to be sorted in the first service pack."