As someone who has experience in IT and is doing a degree in the subject AND who has installed all versions of Windows from Windows 3.1 onwards, I call bull on your theory that Windows 7 is "crap" as you so elequently put it!
Ironically enough, you have listed below several reasons not to buy Windows...
Didn't you even know that the reason why your sister had problems with her laptop wasn't necessarily because of Windows 7 but because it's a Sony laptop, and they have a horribly bad reputation! Also, haven't you thought that your parents may have just had bad luck with their new Windows 7 devices...
Some models of Macs may have had less than stellar reputations, but I don't think there has every been a model that has had a "horribly bad reputation". One of the advantages of the HW and OS being created by the same company.
I own 3 laptops; a HP which I installed Windows 7 Ultimate on, a Toshiba which I've also installed Windows 7 Ultimate on and a Samsung Netbook with Windows 7 Starter, and with all three of them I've never had a problem connecting to a network at all, not even my own home network (my router is in my bedroom and I can easily get a decent signal in the living room without any problems at all!)
You don't need to choose which 'version' of OS X you need. You just buy/get the current one. You don't need to foretell the future to see if in 2 years you need 32 bits or 64 bits.
Out of curiosity, what kind of anti-trojan/anti-spyware software did you install?
Whenever I build a computer system for someone, I always do my research not once, not twice but three times, especially where software is concerned, and definitely where anti-virus software is concerned as a lot of the anti-virus software out there aren't worth the money that's charged for a yearly licence!
Anti-Virus. Arguably a good practice for a Mac user, if only to catch and delete viruses that your Windows colleagues are sending you before you re-send the document onto another Windows colleague.
In other words, I'd rather build a computer system that has quality parts and the OS of the buyer's choice, and if they want Windows, which 9/10 people do, then that's what they want.
If they want Windows.... then good. I don't really care.
Funny story. Several years ago my wife, who uses a MBP, was tele-commuting across 3 time zones. Her office was a Windows workplace, so they bought Mac for Office and everything was fine on that front. But they also required her to use a particular VPN client to tie into their server. It was, of course, a Windows only client.
So we installed VMware Fusion and XP and the client and mapped the server drives so that OS X could see them. Each morning she would boot XP into a VM and sign into the office servers, and work away. About a year later she couldn't sign in. We looked at things at our end. We re-booted everything we could. We re-installed the VPN client. Finally we called tech support in Ottawa.
We discovered two things. One: They had changed the VPN password, and forgot to tell my wife. Ooops. Two: The reason they forgot to tell my wife was because they had forgotten that she was using the VPN. Out of an office of about 40 VPNers, she had not called in for tech support once. Every other (Windows) user had a tech support ticket and that was how they had created their password change contact list. They told my wife that some people were calling in weekly to trouble shoot connection issues.
So, my wife's MBP ran the Windows VPN client better than the Windows machines. But I'm sure her experience was unique, and we can't generalize.