you can hit Apple-Shift to go back to the original App
Er... not exactly. That's what Alt + Tab does in Windows. In X Apple+Shift takes you to the open app that is at the left side in the Dock of the one you are in, which is not necessarily the previous active one. I forgot to mention too that Shift does not work unless you have first used Apple + Tab.
This way Apple + Tab will lead you to the next open app (not the last active as in windows), and 'Apple + Tab' + Shift + Shift will lead you to the previous open app (while in Windows just type Alt + Tab again and you are back there). That is that "simple" IF both open apps are one besides the other in the Dock, but hey "in Mac OS X you do not need to close applications", so prepare to click a crazy combo of alts and shifts 20 times if that is the icon span in the Dock between the apps you want to keep swapping. And do that without forcing your sight to derive from the workspace towards the Dock...
So in your opinion 'Apple + Tab' + Shift +Shift, and having to click either Shift or Tab a variable ammount of times each time to go back and forth, while having to look at the Dock of course, is better than ONE single Alt + Tab to change between two apps repeatedly?
I love many many things of Mac OS X better than Windows similarities, but let's give credit where it is due. Alt + Tab is in Windows since Windows 3 so it is quite normal that they have it more polished than Mac OS. I do not think this has nothing to do with subjectiveness. Windows is simply more efficient with its way of dealing with this.
PS: One could argue that if I plan on working on two specific apps intermitently I could just move one in the Dock to be next to the other, but then the system is telling me what to do instead of the opposite, forcing me to take extra steps which I wouldn't normally do, replacing my 'personal tastes' (I might like it the place they are already), and the Dock will think that by moving a certain open app's icon I am telling it too to make that icon stay in the Dock when i close the app, so yet another unwanted sideeffect.