why?
OP, one question: Why do you want to switch ?
Win 7 was good...Win 8 improves over Win 7.
I have been using Macs the past 6 years. If you had asked me then, I would have told you to go for a Mac straight away. But those were Win XP and Vista days. Mac OS was indeed very stable then.
Today, the gap has decreased due to improved Windows and a less stable Mac OS - (not an assertion, just IMHO). In such a scenario, I don't think it is worth locking yourself in Apple's ecosystem cause it is an expensive affair.
If you go Mac OS, then you have to completely rely on Apple for the hardware too. This is very important to note! Apple does not have a great track record in updating all its product ranges in a timely manner. Case in point, the recent iMac upgrades were long overdue! If you needed an iMac desperately in March, you would have to pay top dollar for a year old tech. If you are in Windows, no such problem...either try Dell, HP or whatever suits your fancy to get the latest hardware. Very often, even if the product lines are updated, they are relatively more expensive than their counterparts even if you account for the high quality materials used in the construction of Macs.
If it is Apple's aesthetics you are after, there is no beating them at it but you have few manufacturers who have come close. Asus ultra books, Samsung Series 9 etc. These are pretty good looking machines.
I will stress on the importance of choice here. When I dipped into Apple's pool, I was blinded by all the shininess.
As of today, apart from the smooth action trackpad, I don't see how Mountain Lion is better than Win 8. Both of them are different operating systems with a different workflow. You will take time adjusting in either case. But one comes with a lot more choices than the other.
Regarding viruses, more viruses are written for Windows than Mac but if you use common sense, you can have a virus free Win system too. Not that difficult.
But if you really want to switch, know that it is quite easy. Apple has something
here.