You don't have issues with viruses because the people who make them don't bother with OS X. People that do that kind of thing do it for attention, owning a Mac is already self inflicted upon the owner, its a waste of time.
And yes, OS X is riddled with holes and security flaws, no one wants to bother with it because it holds no bragging rights.
Who's gonna get more attention? The guy that takes down Microsoft or the guy that takes down Apple? Microsoft, hands down.
If the market where to do a complete 180 and Apple was in the lead they would make Microsoft look like Gods in the who's OS is more secure game.
Got to agree with this to a point.
They to not bother because OS X is what maybe 5% if Apple is lucky.
While I think OS X has holes I would always go with Microsoft having the buggy system.
For two reasons
1) Microsoft does not have hardware control Windows Vista has to work on a virtually unlimited combination of hardware.
2) OS X is based on Linux and contains fewer lines of code. On one the boards I read a member posted a flow diagram for and internet call on Windows and on OS X. You do not have to have a computer science degree to see OS X is clean.
Even this aside I did read on good unbiased article where the author was comparing Vista and OS X.
And Vista does many things better that OS X and the other way around OS X does many thing better than Vista.