I've been using MS Natural Ergo 4000's for the last 7 years now, and using MS Natural's for a few years longer. I've got to say they're wonderful keyboards in general, but they do have a few flaws with them especially when it comes to gaming, which is what I do most with my PC at home. The one particular issue I run into is multiple simultaneous keys, the MS Natural can only handle a couple keys at once before it stops accepting further input. Usually not an issue, but I've found for a few titles lately this is a problem. The other issue I seem to be running into as of late is durability - I learned several years ago MS no longer has a "lifetime" warranty on their peripherals. I don't expect a keyboard to last forever, and I have gotten a pretty good lifetime out of the 3 4000's I had (I retired one about a year ago, retired another last night and will be retiring my last one as soon as I get a replacement - all for the same issue - no longer responding to certain keypresses). I was curious if anyone had experience or recommendation with any other ergonomic keyboard out there.