It's a rather nominal fee, though it might take consumers who are used to the prior free upgrade programs aback. Still, those who sign onto the program will be able to download Windows 8 Professional beginning the day it is made "generally available;" the upgrade also comes with 90 days of support directly from Microsoft.
Of course, free or a nominal fee, there is always some amount of pain when updating your PC's OS. In addition, we always prefer - and recommend - that users perform a clean install, not an upgrade install that might leave dross on the hard drive and in your installation.
To qualify, Windows 7 PCs must be purchased between June 2, 2012, and Jan. 31, 2013, and have a valid Windows 7 OEM Certificate of Authenticity and product key. Upgraders will have to register through the Microsoft site (the link is not yet live) by February 28, 2013. While not free, compare the $15 fee to a standard Windows 7 upgrade, which starts at $119.99.
The Release Preview of Windows 8 is available here, but as an unreleased product, shouldn't be used on a machine that is critical to your environment. Remember, also that the Release Preview will expire. The official Windows 8 release is anticipated to hit retail by October, or perhaps even sooner.