I used to upgrade to the latest and greatest at every offering, frequently having to upgrade my hardware and other software in the process. This goes back to DOS! Everything works good together now so no, I have no intention of changing anything.
The hackers won't be targeting XP any more than they are trying to break into TRS 80s. I have used Vista, 7 and 8 at work and none are as fast or stable as my old dinosaur. Thanks but no thanks.
I will say that in some medical applications I use, the performance of that application under Windows 7 is so far superior to XP that we had genuine concerns about the “word getting out” to those who had to continue to work under Windows XP.
There was that much difference. Granted, much of it was due to the applications being memory bound, but...that is still part of the overall improvement, not just a happenstance.