I used OpenBSD for a few years before switching from XP to OSX, so I've got a few skills that come in handy for making the transition easier. A lot of BSD developers use OSX for their main desktop too.
The people who developed the BSDs deserve a lot of the credit for OSX, Apple really only made minor modifications, and put a simple usable interface on top (OSX can use X and Gnome/KDE if you want)
Every Computer/OS has it's share of glitches:
Sleep problem can be solved by opening and closing the lid again, or turning up the screen brightness.
Fixed overheating with smcFanControl (reboot and the settings carry over into Windows too).
CPU idle whine fixed with QuietMBP.
refit gives me a nice simple boot screen (just Apple and Windows logos), and saves holding keys down at boot, or selecting boot volumes (May try installing OpenBSD soon).
I can reliably crash XP by trying to change the volume with the keyboard, haven't tried brightness yet, as I'm never on battery (Bootcamp /is/ beta).
Playing BF2 for up to 8 hours really gets the CPU and GPU working (screen blanking errors from overheating), so I've built a cooler from a couple of bits of wood and a pair of 40mm fans, pointed right at the underside of the case below the 2 hot spots. Could be Omega drivers tax the system a lot more, as it didn't happen with the Bootcamp or ATI's drivers.
The whole 1 button thing should encourage users to have one hand on the keyboard, as apple-key - click is right mouse button. also means the shift, alt and ctrl keys are handy for modifying selecting and drag and drop.
Apple makes great use of keyboard shortcuts which increases productivity, as it's quicker than dragging a mouse around the screen, and coupled with AppleScript or shell script makes complex repetitive tasks dead easy. I wrote one that ejects the DVD drives, and when a disk is inserted, it creates a folder using the DVD volume label, copies all the files over, then ejects the CD and starts over. Got to love having Unix tools like awk as part of the default system (and grep, ssh, python, perl, top, iostat, netstat, tcpdump, etc.).
AFP makes SMB look really slow, XP on gigabit is rubbish compared to OSX. Firewire 800 comes built in, and goes at turps through a donkey speeds too.
Apache is built in, PHP and MySQL are dead easy to install.
I'm happy to pay a bit extra for a computer that just works, and lets me just work too. Truthfully, the only thing I use Windows for since I got the MacBook Pro is games (credit to Mozilla for Firefox and Thunderbird).