We have both W8 64 Bit and W7 64 bit. W7 is easier to navigate with a mouse and is a solid choice. Better than Vista and even XP. 7 is a shining example of what Windows should be. Hardcore gamers would be wise to go with 7 unless you are trying to make your PC as future-proof as possibru.
W8 works fine though it feels clunky with a mouse. Not the best for gaming in terms of usability, but we havent had any driver/software issues yet...its just the interface that bugs me. Great OS for business and the more casual user though, and many gamers might even like it. Im old school, so I stuck with 7 for my own rig. The kids have 8.