I decided to connect my employer-supplied MacBook to external monitor, keyboard and mouse at work. So I plugged in my Microsoft Natural Ergonomic Keyboard 4000 and original Microsoft IntelliMouse Explorer (still using V1, wow, these things last).
Obviously there is a need to remap control, alt and windows keys to correct mac positions (namely, swap alt and windows keys to match option and command keys). Things didn't work out that great: although OS X Leopard keyboard preferences allow to remap keys on per-keyboard basis (I don't want to remap all keyboards to keep MacBook keyboard as it is), settings are lost if you unplug keyboard.
Mouse provided another surprise: back and forward buttons didn't work in Firefox.
Things looked gloom, I considered writing Firefox extension to handle mouse buttons and started googling ergonomic keyboards designed specifically for Mac to replace my current keyboard. To my surprise, this Microsoft keyboard consistently came up in result at the ergonomic keyboard used by many people on Mac. It turns out Microsoft provides driver for both mouse and keyboard!
After installing the driver it recognized both mouse and keyboard, and allowed me to configure all setting to my liking. Command and option keys are swapped, volume up/down keys change the volume, mouse back button works. Microsoft, you surprised me, thank you for making my switch to Mac so much nicer (no pun intended).