Well, I am a huge Mac fan and I switched a little over a year ago. Right now, I currently own a Mac Pro desktop, a MacBook Pro, and an iPhone. I started with the desktop. Honestly, I switched because Vista drove me crazy.
I had a little Dell desktop running XP since 2005. That little guy was a workhorse but was slow and I wanted to upgrade. So, I went out and got a brand new FULLY LOADED HP desktop running Vista. That thing was a problem from DAY 1. First of all, Microsoft's operating systems are HUGE memory hogs. So even though I bought a brand new computer loaded with RAM, a massive HD, and a screaming Nvidia graphics card, the darn thing was still slow as hell. If I tried running PS and Illustrator at the same time, it would just freeze. Within about 3 months of buying that machine, I couldn't take it anymore and got a Mac Pro.
I was a PC user my entire life, so this isn't about trying to be cool or jump on some sort of bandwagon. PCs just wore me out. In my opinion, the operating system design is incredibly unstable, unsafe (viruses) and slow. You just don't have these problems with Macs.
Yes, Macs are expensive, but there is a reason for that. They are well designed, completely intuitive and they just work. Plus, you don't have to run a huge antivirus program in the background to keep your computer safe.
So, what are some of the tangible differences?
1. They are fast...and I mean screaming fast. As I stated in the other thread, start up on my huge Mac Pro is about 30-40 seconds tops. Same with my MacBook Pro. The new iMacs are supposed to be crazy fast.
2. They are stable. They never freeze up. No blue screen of death. They don't get viruses and don't need antivirus. You can run multiple software programs at the same time without even so much as a hiccup. This to me is huge. Have you ever been working on a layout and all of sudden PS stops working? Your computer seizes up and you have to reboot...only to lose all of your work? That NEVER happens on a Mac. I can run PS, Illustrator, Bridge, Lightroom, Entourage, Messenger, Firefox, iTunes all at the same time no problem. Your software is not competing with the operating system for resources.
3. I don't have to run any sort of antivirus in the background which slows a computer (that means a faster computer and no subscription fees). Also, Macs come with a program called Time Machine which backs up your HD to another drive. I had to used this feature when I accidentally deleted a database in Lightroom and it worked like a charm.
4. Support rocks! Every computer, whether it is a PC or Mac, can have hardware failures. When I got my new Mac Pro, I had an issue with kernel panics. I took it to the Genius Bar and they discovered that I had a bad graphics card. It happens. They replaced it and within 24 hours, I had my computer back, good as new, free of charge. If you don't have a Mac Store near you, they also have service through authorized service agents throughout the country. So, you always have access to support. The standard warranty is a year, but you can pay extra to get extended coverage.
5. Mobile Me - this is a paid service through Mac that I really like. You can sync your contacts and calendar across all of your devices (important for me since I have 3)...and you get an iDisk which is a killer feature. Basically, I can just drag a file to my iDisk and then ANYONE ANYWHERE can access it (you can password protect it, if need be).
I could go on and on but I think you get the picture. You just have to decide what is most important to you. As a paper and digi designer, I had to have a powerful, fast and reliable machine. Mac fits the bill much better than PC. Period. Yes, they are expensive, but as someone said earlier, you really do get what you pay for.
Susan
I really, really love my MacBook Pro! And, they're so pretty too. 
I use a PC and always have.
