if you had said Hyperthreading, then my answer would have been an instant no.
It's been discontinued for almost a year now, but in any case I have never experimented with a dual-core proc under such an old OS, as you would most likely be bottlenecking your system, but your best bet is to try it with Win2K (perhaps the only halfway-decent MS OS in my opinion, along with NT4 and Win95 OSR2). I've actually successfully been able to get an old Athlon XP machine running Win95 and NT4, however, performance is not quite as desirable as with a "newer" OS. And as an analogy, don't bother running a PIII on anything older than 98 if it's optimal performance you're looking for.
Think of it this way: Windows 95 (OSR2) has a suboptimal AGP implementation, do you seriously think that a PCI-E graphics card would function flawlessly under 98?
Even then, nowadays, because it's been discontinued, you would also have to be extremely cautious on what kind of hardware you add to your machine, or even what you're currently using (that is, if you really wanted to run 98), because of driver support.
And on top of that, if you have a very large HDD, the FAT32 partition limitation will easily rape you. And in the end, I prefer the stability of NTFS/HPFS/Ext2 over FAT32.
Oh yeah, also Windows 3.11 boots up in a flash on my old Athlon XP machine, however, being stuck at 640x480x16 colors (since the built-in SVGA driver isn't fully VESA compliant) isn't very satisfying.