It all comes down to risk
If you can efficiently run your business while remaining on old operating systems without compromising security, then power to you.
I run into the same issues at my job. "If it isn't broken, then why fix it?" or worse, "So what if it is out of support. What could go wrong?"
My advice to you is if your clients decide to stick with and old system, make sure they understand the risks so that if (when?) something goes wrong they can't say they weren't informed by you.
I don't see Windows 8 as being in a "buggy state". Can you identify some bugs? I would like to know what they are as I have not run across them. It's different but I wouldn't call it "buggy".
I just see Windows 8 as too unfamiliar for most business users. Unless you have a good training program, you might as well let them buy Windows 8 for home so they learn to use it on their own time. Alternatively, you could deploy it to "early adopters" and maybe it will catch on with the rest. - that's if it works for you.
