I am a recent switcher. Spent FOREVER with every version of Windows since Windows 3.1 and DOS, right through Windows XP. Along the way, I got SO fed up with Windows that I started experimenting with Linux. I quickly took the plunge and went to Linux full time. Over the last two years, I have worked almost exclusively in Linux, keeping Windows around only for Photoshop and iTunes. When it was time to get a new computer, I realized that I could get Photoshop and iTunes on a Mac, and be done with Microsoft for good. This is what I have done. I got a shiny new Power Mac G5 and I love it.
I was planning to load Linux onto this new Power Mac and dual boot, using Linux for day-to-day and Mac OS X only when I needed it, for Photoshop and iTunes, just like I used to do with my PC.
I haven't done this though. Mac OS X is just TOO good. In fact, I haven't loaded Linux at all, and after working with Mac OS X for a few weeks now, have dropped my plans to do so entirely. Why?
Well, lots of reasons. As someone pointed out, with Linux, assembly is ALWAYS required. I am used to this, and not at all frightened of it (I use Arch Linux, second only to Gentoo in the need for ongoing "assembly", but control = speed, and so I do it). With Mac OS X, everything just works, no assembly needed. There is an obvious and graceful way to do everything with no muss no fuss, at least so far. Then, there is the interface itself. It is a thing of beauty. I *love* the look and feel of the Mac OS X interface. On the Linux side, the only thing close is KDE, and it is really a distant second.
Further to this, you can run almost all of your familiar open source programs on Mac OS X. Apple supplies X11, and both the Darwinports and the Fink projects open the world of Open Source Software to the Mac. Just as an example, I went out and got GIMP and am happily running it under Mac OS X!
Then lets talk a real paradigm shift - widgets! What an amazing idea! Once you try Dashboard, you will be hooked. There is no going back!
Linux does have its pluses though. The thing I miss the most is multiple desktops. If I could improve one thing on the Mac OS X interface, it would be that. Also, the Mac OS X window manager doesn't support window snapping, so windows don't snap together when they get close to each other, a feature I really like, and which is on most Linux window managers. Finally, window resizing is pretty archiac on the Mac. You can only resize using one small corner of a window, AND you get no visual feedback (change of mouse pointer shape) when you position the mouse into that area. Even Windows does better than this, allowing you to grab the sides or bottom of a window to change its size.
So, pluses and minuses, but the pluses far outweigh the minuses. My two cents.