No, not anymore. OS X missed the opportunity to become a mass operating system - thanks to its stupid, stubborn, restrictive EULA. There was a small time frame when OS X could have taken Windows' place, at least in the consumer area, and that was during the rather short Vista area where everybody was displeased with that version of Windows. Now with Windows 7 Microsoft is shipping the most user friendly version of Windows ever, and it's more compatible (with the rest of the world), robust and faster than Snow Leopard.
Apple tried licensing Mac OS (not version 10 yet) before 2000. It failed and Apple would have died as a company if Jobs hadn't stepped in and stopped the stupidity of that action. OS X isn't about quantity and no quality; it's about Quality and Quantity with capital Qs. Windows 7 is awesome and I applaud Microsoft for cleaning up Vista, but Microsoft makes more than 90% (not an exact statistic) of their Windows sales from PC vendors, not retail box sales. So far, only I have purchased 7 at a store, and not have it bundled with my new PC. My friends just bought new cheap PCs to replace their 1 year and dying cheap PCs. Windows will never be more robust than any Unix OS, being compatible with everything is what Linux does best, not Windows. OS X works on a carefully selected and tested list of hardware, so Apple has more control over the entire system (hardware and software) and better ensure that performance is at a certain standard. Microsoft can never do that. How can Windows 7 be faster than SL when SL boots faster and uses proven Unix foundations over virus-ridden Windows NT?
The only reason to buy a Mac now is when you really, really want to have that designer hardware on your lap or desk. Software-wise, unless you're a user of the three big Apple Pro applications Final Cut, Logic Pro or Aperture, there is zero reason to switch from a PC to a Mac.
It's not designer hardware. My friend wanted a new computer, specifically a 13". I told him a MBP 13", but he also wanted to compare HP's Envy 13. He likes HP and Lenovo brands. We got together at his house on day and configured both computers to match his budget. The MBP 13" was about $500 cheaper than the Envy with as almost matching configurations, we couldn't make it 100% exact (as much as we could) but the main components were the same. He showed his parents (accountants) and they bought him the MBP along with a refurbished 24" ACD display. He got all that for about the same as 1 HP Envy 13. Later his parents needed new computers and bought Macs because they got tired of buying cheaper PCs and just wanted quality, Macs or PCs. Macs were cheaper with comparable PCs.
Also, your statement is wrong because if that is the only reason to switch, how do you explain Apple's increasing quarterly reports? They always make more money/revenue than last year of the same quarter. iPod sale have peaked already and iPhone sales haven't increased enough to make this happen. This has been happening for over 4-5 years. Prices have actually lower than before too.
Unlike what Apple's marketing machinery wants you make believe, there are counterparts for everything the small Apple software market has to offer, and you can run it on machines that only cost a fraction of what a Mac costs. I just saw a Quad Core AMD Phenom machine for 500 bucks with an ATI graphics card with 1 GB of video memory. At Apple, customizable machines with that horse power begin beyond the 2300 Euros price tag. And I doubt that the Mac Pro would be really that faster.
First off, AMD processors are totally different than Intel processors. Just like PC vendors have different business plans than Apple. That PC you mentioned performs well only in certain fields. Macs perform better all around, not just CPU or GPU benchmarks. It's a complete system with quality hardware in every area, not just a few areas. I could buy a $10 million house but fill it with a few pieces of furniture and lack in certain areas or I could have a $5 million house with quality furniture everywhere around the house.
Apple pays attention to every aspect and detail of a computer, not just the CPU and GPU. Macs have aesthetically pleasing designs, fast processors, fast graphics, etc. That AMD machine only has a fast CPU and GPU, but what about other components of a computer? Probably the cheapest components and lacking in quality.
So, no - it's only the design and the designers' love for details why you purchase a Mac. There's nothing wrong with that. Apple sells good PCs. A bit pricey, but nice.