Not been using a Mac very long and have come from a background of other compute platforms.
However, without going into too many details I used to work in a security organisation where I had to assess security of various compute platforms.
And though there are fewer Mac malware attacks the platform is not immune. There are a number of subversions available via Safari for-example.
Personally, I do run Clam on my Mac because I believe something is better than nothing. Mind you I have only just started using the platform and so I may well improve on Clam when I understand more about my risk profile.
I don't bank online and try not to leave any personal information in cookies etc that can lead to significant personal exploit.
You should enjoy your Mac as it is a beautiful thing. Apple and security are a little frustrating, for-example, they have some good approaches and some poor ones (they have a great crypto hardware design in the iPhone but they don't fully utilise it for security).
I'm not into comparative rants about different platforms having varying levels of security as all platforms have their weaknesses.
I would just say take a look at the kind of activities you intend to use the machine for (honestly assess whether your or a partner's behaviour may merit additional protection), the environment your using it in (at home, in an office with shared wi-fi, in Cafe environments, etc) and then make your own decision.
All the best,
Sam.
