Good build but one point, if you plan on overclocking the CPU later, I suggest you choose another motherboard, the one selected has a weak 3 phase VRM set which is fine for stock speeds but not really suitable for overclocking.
Win 8 is really the way to go for a new build, is there any way you can get to a Win 8 system and try it out? Friends? school? work? or just drop into a large computer store and play with their demo systems to get the feel of it before making a decision.
Point on the OS: Retail versions are more expensive but you can migrate the license to another system later or keep it if you upgrade the MB/CPU (Microsoft regard the MB/CPU as being 'the computer') and offer some tech support, OEM licences are less expensive but are locked to that particular MB/CPU and have no tech support.