...unless you are still running XP on a P4. Then, you should upgrade)
P4?
Hey, I sold my Phenom II a couple of months ago, and bought an i5 for my Hacckintosh.
But I've still got one machine with a PIII (@1.5GHz)!
And another with a Socket A Athlon!
Both of those are going to continue to run XP for pretty much forever.
And I have Win7 on the i5 Under Parallels.
Why would I want to upgrade to Win8?
On the two old machine, upgrading the OS to Ubuntu would be more economical then changing the hardware.
And there nothing offered by Win8 that would improve the Hackintosh.
Win8 might be a great product if you're running XP or Vista on relatively modern hardware, otherwise why bother?