I'll respond and actually not lock it, only because its an interesting discussion. The discussion is no longer relating to YOUR computer purchase anymore obviously, but is still a perfectly resonable discussion.
I think the issue many folks have with Dells, myself included, is that the parts between their own machines aren't standardized. Which makes repair and replacement difficult. Upgrading is still usually feasible.
However, regarding the Mac OS, its a fantastiaclly stable and usable operating system, but if you spend most your time on Windows, requires some getting used to. But now is a better time than ever to go Mac...they've updated the iMac line just this week to a very sleek look.