there are not very many russians writing viruses for a relatively small population of macs. if mac OS were the international corporate standard for computers, the tables would be flipped and there'd be many more viruses for macs and more effort expended to compromise macs. their relative lack of popularity is their biggest advantage against viruses.
as far as ipads and iphones go - they are more like appliances in their design than computers. they perform like a toaster - turn it on and use it. its not really the same as a desktop computer OS experience.
Personally i find android to be overall buggier from a software dev POV and from a user's POV. to me, and this is my opinion only, this is due to the fact that, like windows, Android is meant to run on a number of hardware configurations - there are a ton of manufacturers making devices that use some flavor of android - some will work with one version of the OS but not others - some will run android better than others.
this is not the case with Macs. the inherent advantage (or disadvantage depending on your POV) of Macs is their vertical integration and closed ecosystem - the hardware and software are designed to coexist from the beginning. in the case of i-devices, they are built around the OS and vice versa. its been my experience that the hardware tends to remain relevant for longer periods... people are still using 10 year old macbooks without major issues. not too many 10 year old windows laptops still able to keep up however.
You dont really see this with any other consumer devices of this nature. This makes the test-bed for the software developers relatively predictable and stable - you can ferret out more bugs in development because the device universe is known and relatively uncomplicated. unit testing and regression testing is more straightforward.
Virus threats may soon become something more to worry about on Macs. if the trend of PC users permanently switching to MACs continues.
I will agree, if you are heavily invested in windows machines, then an iphone may not be best for you - i havent found itunes to be all that reliable on windows. on mac its a different story in my experience. anecdotal as it may be, it seems like the popularity of idevices is really driving the switch from PC to Mac. Users have a strong and positive first experience with an apple product now via these idevices and then set about making larger changes in their lives and adopting the Mac platform across the board. My parents in their 70's did exactly that. got an itouch, that led to two ipad2's and a 27" imac, all happily coexisting with automatic time-machine backups, easy networking, and cross-device synching of everything from their address books and calendars to their photos, movies, books and music.