in games windows 8 is only 1% faster than windows 7.
windows 7 is supported by a WIDE range of apps and games,
there might be a lot of unknown issues in windows 8 reagarding compatibility too.
plus u have to get everything from the appstore to show in metro UI
i used it and it takes a LOT of time getting used to.
i say u use dual boot and keep windows 7 as the main OS and maybe use win8
side by side to slowly get a feel of it, so that u can decide. if u like it or not