Linux/Unix is a very different world than the PC/Macs. Comparing them is not comparing apples and oranges. With OS X, the two worlds have begun to merge. If it weren't for the proprietary HW requirements, and expenses, I'd be using it at home already - the ad campaign for transitioning is good, but it would still cost me way too much to convert from Win98. Windows is great for mail, MS Office, games. Mac is great for video and photo manipulation, non-computer-savvy, and most day to day activity. Unix is great for networking, stability, and versatility (routers, firewalls, file management, back-end servers, etc...).
So, I say there's room for all. I wouldn't want a Jeep in the suburbs, a Porsche in the mountains, or a volkswagon to haul timber. For the same reason, I wouldn't want to be limited to Windows OR Unix OR Mac (OR mainframes, handhelds and embedded devices, supercomputers, or clusters, for that matter).
I've never much understood these arguments.