Well, the thing about OSX is that it is heavily reliant on in house media codecs and drivers that I find haven't been virtualized very successfully so far. Furthermore, I find that the (paid) virtual host desktop solutions on OSX are much better in terms of performance and integration than their windows counterparts - probably because of higher demand, possibly also because of architectural reasons.

But maybe you have found a way and you can then prove me wrong: Does iWorks work in your virtual box VM? Does XCode including iOS simulator work well? Is the performance acceptable? How about the iLive suit? How about unity development? How about the clipboard - does it keep its 'PDF snippet' functionality (no rasterization of fonts, original quality images)?

See, there's tons of OSX exclusive software that's quite demanding in terms of media and hardware acceleration, simply because of the OS's highly integrated character. Unless someone can show me a solid OSX-in-a-box I doubt that it's a good experience.