Depends on the price.
From what Ive read, having more than 8 threads may really benefit thenewer OS, Vista al lil and W7 alot.
Itll be interesting as we head into +8 cores to see whether 8 true cores vs HT or AMDs solution benefits the newer OS'
Right now, XP currently operates a lil faster under 8 cores, but after that, since theres better usage of MT at 8 and over cores with Vista, and even moreso with W7 due to their respective superior handling globally on MT, we may finally see some nice returns across the board have more cores, and then IPC may take a back seat to many cores