Baby's gonna be up any minute now, but let me see if I can answer the questions.
Before I even start, yes, you can buy a mac and have a perfectly good user experience, and if thats what you're familiar with and what works for you, keep buying them.
You can go to the network associates virus pages and do a search there for mac viri. One guy did that and did an interesting rationalization report. He found 612 viri that affect the macintosh. He 'decided' that some of them werent really viruses by his definition (which is a little hard to agree with), took out a few dozen that only affect classic mac apps (which do run just fine on os x so you really cant take those out either), and then took out any that had anything to do with microsoft applications running on the mac. By the time he was done winnowing out everything (which I believe was his intention) he came up with zero. Note that this list he used did not include any bugs in os x that were acknowledged and repaired by apple.
By applying the same criteria to Windows, I believe the number of bugs still existing and unpatched by the manufacture, excluded of things I whimsically decide shouldnt be included, caused by apps made by another company, or primarily affecting older unpatched versions of the OS, the number is also zero.
You should have an up to date virus and spyware scanner for any machine; mac or windows. You'll get by better with the mac, I wont dispute that. But you're not 100% safe, 90% safe, or even 4% safe
On a windows machine of quality construction, with just the operating system and the core apps installed, you will experience the same level of quality use and stability one gets from OS X and a mac. I have a cheap home-built machine of no pedigree and XP, it doesnt crash, it only does funny things when i've just installed a new piece of software where the fault lies with the software, and i've never had to reinstall the os in many years...even though i've installed and removed thousands of pieces of software.
Mac mini - MSRP $499. Current Dell PC offering, $299, which includes a monitor, keyboard and mouse which I believe you have to add to the mac mini...?
Just to redux (babys still snooooozing). Macs are good. You add a bunch of funny hardware and software to them, they'll have problems. "regular" pc's are good. You add a bunch of hardware and software to them, they'll have problems. Ounce for ounce of computing power, you'll pay less for a "windows" platform than a mac platform. Usually half. You may or may not find an app you want to run in a mac version; usually what you want will run on a pc. Macs are more stylish than most pc's, but if you want to pay for a pretty box, chances are someone makes one that runs windows that you'll find appealing.
You may hate bill gates and microsoft...thats ok...they're eminently hateable. I've met and spoken with both bill gates and steve jobs many times over a period of decades and sat in business meetings with both of them. If steve jobs was in the position bill gates is in, trust me, you'd hate him and the company he ran more.
The only points I wish to make is that there is nothing "magical" about a macs hardware, software, build quality or manufacturers "quality". In equal settings, both serve well and both exhibit the same approximate level of "badness".