If you're running Windows XP, Vista, or 7, you'll be able to upgrade to Win8 for just $40 when the new OS becomes available on October 26. That's for a downloadable copy, by the way. If you want a retail-boxed DVD, you'll need to shell out $70. According to the official Windows blog, you can pre-order those retail upgrades starting today. Newegg is now accepting orders for the Windows Pro upgrade DVD.
What if you're building a new system and don't have an old Windows license lying around? The full versions of Win8 are available for pre-order, as well. Windows 8 costs $100, while the Pro version runs $140. Those are OEM licenses meant for system builders; Newegg doesn't seem to have the consumer-friendly retail boxes available right now. It does, however, offer a "Pro Pack" that upgrades the standard version to Win8 Pro. That option costs $70, which seems pricey given the $40 delta between OEM versions of the two operating systems.
Windows 8 comes in 32- and 64-bit flavors, and Newegg has 'em both. It's hard to imagine folks with 32-bit systems itching to upgrade their OS, though. Seems like it would make much more sense to simply offer both flavors of the OS on the same DVD.
I suspect most enthusiasts making the transition to Windows 8 will opt for the $40 downloadable upgrade. I've had a couple of non-techie folks ask me about it in the last couple of weeks, too, so the word seems to be circulating outside the usual nerdy circles. I'm still on the fence about upgrading my own desktop PC, however. The OS has a handful of desktop enhancements that look really sweet, but I worry that Metro will taint the overall experience.