I worked (albeit briefly) as a "genius" (god I hate that term) and as a "sales associate" at an Apple store (SoHo, NYC to be precise). As I have worked in Windows for years (building systems, programming/coding, and then with OS X), my opinion is both have their strengths. Each system has their own pro's and con's (I have Windows Vista running beautifully on a SATA drive on my Mac Pro for work), the difference is SOFTWARE. Not getting into specifics, but generally speaking when comparing a Mac system to a Windows based system, you don't need all the extra protection software and antivirus subscriptions bloating your system and generally slowing down performance. Mac's don't require defragging and optimizing to make them run as they did when first purchased. I have gotten newer versions of OS X to run on very old PowerPC systems, without spending any money on hardware upgrades, and running faster and better.
While working at the Apple store, I was amazed at how many people came in upset with their Windows systems. Most were blown away by such concepts as "Time Machine" (I spent the evening working on a clients HP system that was two years hold with an Intel Core2Duo processor and 2 gigs RAM that had numerous trojans and adware even with updated McAfee and had to quarantine and eventually zero out her hard drive, and she had NOTHING backed up. I showed her "Time Machine" on my MacBook Pro and she was blown away by how user friendly and simple it was to backup everything and restore it), Exposé, hell even OS X's simple Mail program that works with just about every mail carrier without using a web browser. These little things that most of us here take for granted, Windows users fall in love with over and over again. That's why I enjoyed working there, it was not curing cancer, but it made my clients' lives so much easier.
People who switch over say they do not regret it because of the time and money they save LONG TERM. Upfront you may be saving money, however over the (general) course you spend more money and time trying to fix all the things that do go wrong with a Windows system. You don't need Office or iWork (and iLife comes with every Mac); iCal, OS X Mail, iPhoto, iDVD, iMovie - they all come with the system. Similar consumer based software requires additional costs.
Bottom line, you may save money upfront with a Windows system, however you spend more time and money over the average usage of a Windows system then you would with a OS X based machine. Would you rather own a computer that requires more money and time to operate, or one that would allow the ability to get more work done and spend less time on the computer and more time enjoying life?
(not to mention Intel Mac's can run both OS X and Windows - and didn't PC Magazine rate the Mac the best machine to run Windows in 2008?)