As some people know, I've been addicted to Microsoft's Natural Keyboard (the original), since I got it in 1995. Heavy enough, but a decent key feel as well. I bought up several of them on eBay, and have kept them in the closet for years. I even got one of the limited-edition black ones.
But my favorite one (the one I bought in the company store at msft in 1995) went dead last year, and I started using one of the ones from the closet, which was a little bit -- stickier. The keys weren't worn down in the same ways, and it wasn't quite as comfortable. I had an old pair of shoes problem.
In the meantime, Microsoft has come out with many inferior keyboards, including the Elite (too light and flimsy, and I broke the pads off the bottom), the Pro, which has funny layout and squishy keys, and most recently, the Natural Ergonomic Keyboard 4000. Yes, Microsoft's marketing & naming machine has gotten even more extreme since 1995.
I was looking around recently because I got a new computer, and I ordered the cheapest possible keyboard, figuring I would once again keep my old 1995 keyboard. But this cheap keyboard surprised me -- the keys felt good and they were curved in a subtle way to make me like typing. So I started wondering if they'd done an update to their split/ergonomic line...indeed they had, and I ordered the Microsoft Natural Ergonomic Keyboard 4000. It comes in a big red box, which says, Microsoft Natural Ergonomic Keyboard 4000, just in case you were wondering.
I did this with a bit of trepidation, because this keyboard does have a "My Favorites" button, and it does have funny extra buttons along those lines-- not as many as earlier editions, but enough to be annoying and to make me think the keyboard doesn't take its job seriously.
But...it's quiet. And it is really nice to type on, really quite nice. And so I'm keeping it, and I don't have to keep hoarding eBay finds from 1995 anymore.