I was a PC user for a very long time - since DOS 3.3 (around 1988.) I've been through all of the various versions of Windows (Windows NT 4, Windows 2000, XP, and now Windows 7 being the "best" ones for their time), Linux, and even OS/2 (but that's going way off subject

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I finally started to get interested in switching in 2007 after becoming sick of having to "deal" with Windows all the time. If it wasn't viruses, it was having to maintain the OS, or dealing with random bluescreens. The list seemed pretty endless.
I've never been what you'd call a "gamer" - I play some MAME arcade games here and there, Plants vs. Zombies, stuff like that. I'm more interested in Photoshop, so I felt the Mac would be a better platform for me.
Bought my Mac Pro in early 2008, and was absolutely thrilled with OS X. A much more stable platform, built on top of UNIX (having a Linux background helps too.) "Maintenance" on the Mac is easily accomplished with a small program that runs the daily, weekly and monthly cleanup scripts when necessary, and the hard drive doesn't need to be defragged nearly as often (if ever) as it would help a Windows system.
I've found the Mac experience to be overall more satisfying than I *ever* had with Windows - the computer is nearly silent, always fast, always up to anything I want to throw at it.
Having built-in utilities like Time Machine (great backup software), Spaces (virtual desktops...I can't use my Mac without them anymore), ease of installing programs (drag a file into your Applications folder...DONE), quality of materials and lots more little niceties that Apple included that Windows doesn't is what makes the so called "premium price" worth it to me.
Knowing the Mac version of Photoshop (basically the shortcut keys) is helpful if I ever want to get into doing professional image editing, as most shops I've seen use the Mac version (the keyboard shortcuts really are the *main* difference though - otherwise the programs are essentially the same.)
All this being said, is OS X perfect? Of course not. It has its quirks that I still don't like after 2+ years on the platform. Are they "magical"? God no. I can't stand Apple's marketing terminology lately.
It's a solid computer with everything I want and need, and it's up to you to decide if it's right for you. If you're going into graphic design, it would certainly be a safe bet to buy a Mac and learn programs on it so that you're familiar with them, because it's likely that a future employer in that industry would be using Macs also.