>windows from different desktops in OSX are mistakenly combined in the same useless giant Alt+tab list

Completely agree. In particular, I used Gnome (2.14 through 2.18) for a few years, then OS X (Leopard through Snow Leopard) for a few years, and the way "tasks", applications, windows and workspaces are managed on Gnome strikes me as objectively better than the way they work in OS X -- with the possible exception that the OS X might be a little easier to learn for users that have very little patience for learning much at all about their computer.

But OS X is better at sparing the user from tedious admin hassles and has better aesthetics. Gnome 2 on the other hand allows the user to set the text size of almost all of the text on the system (the most notable exception being Firefox, which does not pay any attention to Gnome's settings), which OS X does not allow. (Some of the text on OS X, e.g., in the menu bar, window title bars and certain Apple applications like Calendar, cannot be changed with reasonable effort.)

Also, the "annoying glitches" on Gnome are worse. The annoying glitches on OS X consist mainly of the UI becoming unresponsive at unpredictable times (usually signified by the spinning beach ball cursor) whereas the annoying glitches on Gnome 2 consist of inattention to detail on the part of Gnome 2's designers and implementors, lack of consistency including "gotchas" like Ctrl-W having minor mostly-reversible effects in Emacs and in bash while having drastic irreversible effects in other Gnome apps (namely, closing the window). Also, Gnome would freeze, crash or otherwise need to be restarted an order of magnitude more than OS X does. Note though that Gnome and the graphical system on Linux might be much more reliable with a different video card: I only tried it with two old cards.