Macintouch has a long series of letters aguing for and against moving the Mac OS X foundation from Mach/BSD onto Linux. They miss the point. The people who favor BSD favor it for the wrong reasons (minor technical benefits). The people who favor Linux are ignoring the problems (the cost and difficulty of porting everything this late in the game). The main benefits, so far as Apple should be concerned, are marketing (“Linux Linux Linux!”). Some people argue that there is an additional benefit of getting access to Linux apps, but that’s misleading: the open source UNIX apps are already available, and the closed source apps won’t run on OS X because the Mac hardware is different.

Wes Felter has more to say on the subject, and links to even more.