The home edition seems like a reasonable buy, but the other versions are pretty insanely priced, IMHO.
I'm still running Office X on my folk's iMac... 2004 on mine. I see no reason to upgrade. Of course, all of my macs are PPC... guess I'll upgrade to get universal when I get a new intel-based mac.
I run 2004 on my Intel MacBook, and it runs fine. I don't see any reason to upgrade to 2008, personally, and the fact that they are removing VB support is a killer.