You don't want windows 8 unless all you do is watch YouTube videos and email if you ask me. But if you are a beginner with computers I would get it.
I have been using Windows 8 for all the same tasks that i would windows 7 for the past month now and have found it to be just as good if not better than Windows 7 and I do much more than use it for just email and YouTube.
but for upgrade i believe it is only on new systems. but they will have cheap upgrades either way for a while.