I started using linux with Slackware in 1995 just before Windows 95 (wasn't it once called Windows '92?) was released. For the next ten years I used every single window manager under the sun. Window Maker was very nice and I used it for years. I never could get used to KDE with it's myriad of options (I used only 25% of them anyway). KDE had such a windows-is feel to everything.
I eventually settled on Eazel's Helixcode which became Ximian Desktop. Ximian was the closest thing I could find to a 'best desktop environment'. Somebody was finally getting the desktop right. In spite of my wonderful new desktop, I *still* had to find and write custom scripts to get wireless to work on my Dell Inspiron. Something as simple as getting a USB drive to mount and then automatically appear someplace accessible was another aggravation. I was stuck in a hell of apt repositories whenever MPlayer wouldn't read this new movie format or when xmms couldn't understand that audio format. I almost always ended up compiling from source (just try compiling MPlayer from source sometime). I came to hate the endless tweaking to keep my ximian desktop running smoothly. I was getting less work done everyday maintaining my desktop.
I switched to OS X on a Powerbook a little over a year ago in October 2005. It was the first time I ever even saw an Apple computer. I must say that I am completely and utterly happy with OS X. I primarily develop PHP apps with Zend IDE and having Apache preinstalled was a nice feature. MySQL was a breeze to install. There is even a nice GUI tool for starting/stopping mysqld. The networking features are stellar. I absolutely adore iTerm and it's tab/profile features. Wireless just works and the iLife apps are something I use everyday with my digital camera and Panasonic Mini-DV at home. Just plug them in and The Right Thing Happens! I use Expose and dashboard at least a hundred times a day. People complain about the Dock but I find it versatile and handy as hell. I missed focus-follows-mouse initially but I adapted. From linux I really miss sshfs, groundbreaking tool that it is but something will come along soon that fills the void in OS X. So many open source inspired tools are available in OS X that I used in linux. It's not really all that different. Bash is still there along with tcpdump and sed, awk and friends. It's the best of both worlds (for me).
Although I was a linux zealot for ten years who heralded the flexibility and power of linux, I tired of incessantly tuning my desktop. I run linux only on my servers now. It is perfect for that. Mac OS X is a beautiful and functional desktop UNIX environment in my opinion. But that is just my personal opinion.
I am no longer a linux zealot. I am not a Mac zealot. I have learned my lesson. Use what works for you. Use what makes you happy. I, for one, will use OS X as long as it is around and continue to enjoy using it.