There are pros and cons on running OS-X (even on Apple hardware).
On the pro, we would all agree on the eye-candy OS-X provides us with.
There are some cons however, the one most striking con is the outdated "finder 7" style header bar, which still is present in Mountain Lion today. Why do I have to activate an application first, before I can close it?! This is really not up to modern standards. Yes, one can close a window on its decoration, however this will close the application only in exceptional cases.
There is still this argument about application, especially for artists, available on OS-X only. Honestly, I am not too sure about this at all. The Linux community seems to be catching up in a high pace. Seen the applications available under "AV-Linux", the Mac world locks rather empty and expensive.
Regarding the look and feel, in terms of OS-X pros, today, there is severe competitor to the Apple operating system. The (free) OS is called "elementary OS Luna".
I played for some days with this Ubuntu based system, which in terms of eye candy comes very close to OS-X. Check the review on DistroWatch.
My personal experience with this Linux distribution is very positive in terms of the experience being very close to what my settings on OS-X would be, without the above mentioned depreciated finder-7 retro-experience Mountain Lion still provides today. Actually, I personally prefer the elementary OS Luna experience over the OS-X Mountain Lion experience, in particular since it avoids the clumsy retro experience of the header bar.
In terms of available multi-media applications, linux is catching up fast, cf. AV-Linux. Since elementary OS is based on Ubuntu, which is based on Debian, the Ubuntu and the Debian software repositories are available, providing an extensive range of applications.
In addition to the above, there as an elementary OS community, providing cool tools such as elementary tweaks, which helps to shift the elementary experience even closer to OS-X.