That's not a bad deal actually. This past Black Friday I bought Windows 8 Professional (non-OEM) for $55 but in general the price of it was lower back then trying to convert people to switch. The price you listed for 7 Professional is the cheapest I've seen that in a bit, usually it's the Home Premium going for $79.99. However, most store retailers no longer carry Windows 7 at all which if you are dead-set on 7, definitely limits your options for sales in regards to something like a Black Friday.
One other thing of note, the latest version of Direct X is not going to be compatible with 7 which won't affect things anytime soon, but might in the future in regards to games so something to think about. Personally, I just built a computer for my dad and have him using an old copy of XP for now and I am waiting on a holiday sale for Windows 8 Professional. I think it will happen around Black Friday and/or when they release the new version of Windows 8. So if you want Windows 8, I would wait for a better sale in a few months. If you have no interest in Windows 8 at all, I would buy the sale you linked as that's a very good price for Windows 7 Professional.
