I cannot say for sure if it would be a waste of money, I think that might be a little over the top saying that. I have not used Windows 8 yet, so I can only offer what I have read others saying and/or reviewing.
From what I have read, Win 8 is great to use on a tablet, but not so great on standard desktops and laptops. The thing is, it was built with touch in mind. So if you want Win 8 and are buying a new laptop or desktop, my suggestion would be to make sure to buy one that is touch enabled. Of course touch PCs usually tend to cost a lot more money, though. The thing is also, that most people don't use touch for everything on a desktop or laptop.
It also depends on how adept you think you are at learning new technology/operating systems. If you learn pretty quickly and easily, then I am sure you would learn Win 8 pretty easily. It's pretty much been rebuilt and there are many things that are totally different than in previous versions of Windows. So I just equate it with learning a new OS. I have seen many tech reviewers, though, say that it's an awful experience on a laptop or desktop, not every one of them, but a lot. What you might want to do is go to an electronics store that sells PCs installed with Win 8 and try it out first. See if you even like the look/feel of it and see if you think you can learn it.
Personally, from screenshots that I have seen, I do not like the look of it at all. But this is just my personal preference. I like a nice, graphical, user interface.....I really dislike the Win 8 tile thing and the colors. It just doesnt look nice to me. Of course the look has nothing to do with how the OS works, but the look matters to me somewhat.