Either technique has become more accessible, whether evolution has to win, then I became an adult, but there has long been the primary OS at work and at home has become OS X
The evolutionary path of OS in the workplace was so:
DOS (5.0 ... 6.22) -> Windows 3.0 -> Windows 3.1 (1) -> Windows 95 -> Windows 98 -> Windows NT 4.0 -> Windows XP (I have not forgotten about Windows Me, Windows 2000 and Windows Vista, just not used)
Next, the path forks:
Ubuntu 8 (9, 10, 11) - at work, at home
Windows 7 - at home