Market share isn't Apples's objective. Their objective is furthering the usefulness of technology in everyday people's lives. I've been a system admin for more than 15 years. Comparing Macs to PCs is simply media bantha foodo. It get's us talking. The reality is Apple's business model gives them predictability, after all they make the Mac OS and the Mac hardware.
The PC market is controlled by Microsoft software. Thus Windows will run on anything. In fact Windows runs better on Intel Macs, as Apple has done an excellent job with windows drivers. However, until windows rewrite Windows from the ground up (they are carrying at least 10 years of legacy code), thereby getting rid of the Active desktop, the registry and .dll files, Windows will continue to have the same problems.
So it is unwise compare McDonald's (Windows PCs) to Dave and Buster's (Mac). The business models are different.
I love computers in general and I have built my own PCs and Hackintoshes. The Mac OS runs better, faster and more stable than Windows XP and Vista. The jury is still out on Windows 7, but I have already experienced several blue screens of death. The fact that viruses are or aren't being targeted towards Apple isn't relevant. The fact is I don't get viruses on my Macs, Linux or Ubuntu machines. These are the facts, so unless these security experts are taking notarized statements form hackers whom claim they don't target Macs because of market share, it's just an opinion not backed up with facts.
Besides the problems with Flash and MS Office, macs are pretty stable.
PCs can be stable as well, if you learn the truth about them (and Microsoft).
The fact is PCs don't come out of the box stable and secured, users have to take additional steps and if they're smart spend additional money on security. Plus you still have to be careful on wireless networks and websites (which is why it is recommended to avoid IE).
I'm no expert. I believe you in using what works best for you. Whether it's a PC or a Mac. You don't need an expert to make your decision. Use the internet and research for yourself. If you an Apple store close to you, pay the a visit. If you have a Microcenter close to you it is a great place to visit for PC stuff.