Years ago I had a Microsoft Natural Keyboard Elite keyboard that I really liked, but they are discontinued now and I'd rather get a new model if it is better or comparable.
The split one is the Ergonomic model, that's probably what they're talking about. I just switched to the same one from a fairly nice mechanical keyboard and it feels a lot better.
Mouse: Microsoft Wheel Mouse Optical 1.1a USB on Mac and PC
Keyboard: Microsoft Comfort Curve 2000 on PC, Magic Keyboard (2. Generation) on Mac
I really like the MS Wheel Mouse Optical, unfortunately it is no longer produced. I tried different mice, but I think I like it that much, because it has lower DPI (400 DPI) than an average mouse (about 1000 DPI). Nowadays it is difficult to get a mouse with 400 DPI.
Got another Ergodox after hankering to try it again after selling my first after a couple months, waiting until I have a little less work to transition over to it as my WPM drops to about 10 while I'm learning.
I use a Logitech Wave at the office. It's not a fully ergonomic keyboard, but has a slight, well, wave. It's comfortable to use all day, but isn't too drastically different to affect my typing style on a laptop keyboard when I get home.
I had an ergonomics issue that Microsoft split keyboards resolve.