Eugene's observations

In a word, yes.  You're probably aware of the commonly used arguments against this: that Apple Store software is curated and thus harder to impregnate, also that there are so few Macs that the bad guys are more likely to target the lower and more plentiful fruit that are Windows PCs.  Both these points hold less water as the months go by. 

There are plenty of OSX ready packages that can be found from outside the Apple store now, for each of these you must trust not only the intent but also the quality of protections implemented by the supplier.  Many infections come as Trojans and therefore bypass the Apple Store security as the end user inadvertently invites the infection.  It is true that OSX is sandboxed by design but this cannot be considered as more than just another hurdle to the inventive and determined hacker.

 As time goes by Windows is becoming more secure and the number of Mac installations is increasing; also Apple computers, being more expensive, are typically owned by the more affluent  - facts not lost on would-be felons. 

There are cheap and easy steps that can be taken to give the bad guys an extra challenge: ensure that the latest updates to OSX and applications are installed, and be wary of browser plugins and other 'free' software that add high risk platforms such as Flash and Java (the default on latest versions of Safari).

 There are two suggested protective programs: Avast Free Mac Security and Bitdefender Antivirus  for Mac.  Which you choose depends on your appetite for risk, the effect that an infection would have on you, and the thickness of your wallet.