I've used a PC keyboard on a mac for years. At first, I used DoubleCommand to swap the windows and alt keys to be in the same position as mac keyboards. Now I just use the keyboard preferences. Recently they updated it to remember devices. Before, I'd have to go to Prefs->Keyboard & Mouse -> Modifier Keys each time I wanted to change from using my pc keyboard to the laptop keyboard. Now, the preferences remembers devices I plug in and lets me set up my modifier keys.
The main difference is going to be the lack of an eject key, but you can press and hold F12. For power off, press ctrl-F12. You might miss the media keys (volume up, pause itunes etc) but I live without them.
The keyboard I use all the time isn't ergonomic, but has a very nice key action. It uses brown cherry switches to make a less mushy response than the apple pro keyboard. It's called a Filco Majestouch Linear.