(This review is based on about 30 minutes of use I'm giving it a week to test-drive and decide if I'm keeping it.) I bought the Microsoft Natural Ergonomic Keyboard 4000 this evening, in my ongoing quest to find a good Mac keyboard. It is not a Mac-specific keyboard, but it meets my other main requirement: ergonomic. It's a split keyboard, which I've been using for years and find more comfortable than the traditional, straight keyboard. It's also wired; my previous try was wireless and it didn't work well. Though not Mac-oriented, it has a nice utility to configure it for Mac Use. In particular, you can swap the Windows and Alt keys to match normal Mac usage: Alt, next to the space, becomes Apple-Command, and Windows, further left, becomes Alt/Option. It has other programmable fun which I set up trivially. Press them with the Preference open, and you're prompted to choose behavior. So in a few minutes, Web starts Firefox, Search triggers Spotlight, Mail launches Mail, and the soumd controls work as expected. I also set the Function keys to run Expose and Dashboard as normal. And I'm tempted to set them to the new arrangement introduced in the new Mac keyboard. Also usefull, there are dedicated Forward and Back keys below the space bar. I'm a long-time Alt-Left and Alt-Right typer to jump back and forth, so this feels like an improvement to me. The negatives... The keys are mushier than I like. My previous MS Natural Elite was perfect. A good throw with a distinct spring release. Also, the space bar is apparently actuated and supported dead center only. Pressing from the sides, as I do, is a bit sticky, noisy, and less smooth. Again, the Elite spacebar feels smoother in all ways. And being a Windows-oriented keyboard, the Functions keys are labeled with WIndows shortcuts (New, Open, Send, etc.) that don't match my Mac uses. Finally, the Zoom Slider just doesn't work in iPhoto. Finally, this elevated, split style is more different than I expected. It will take some adjustment. The MS Natural Ergonomic 4000 keyboard is a nice keyboard and worth trying if you're looking for a full-featured ergo keyboard for your Mac. I'm not wholly sold on it yet. I have to see if the changes in the ergo style suit me. And the space bar just bugs me. But I have a broad dislike of Apple's keyboard and mouse design and deeply wish they'd join the world in the new millenium and make an ergonomic keyboard. Until then, I'll be getting my keyboard from Microsoft or Logitech.