But one day I had to do some maintenance on some random computer in a closet at work, and the only spare keyboard we had sitting around was one of the old Microsoft Natural Ergonomic 4000's, and using the split-wave layout was a revelation. I was officially intrigued by ergonomic keyboards. I've since tried typing on a Truly Ergonomic and an ErgoDox, looking for the sweet spot between mechanical and ergonomic, but it just wasn't the same. I have yet to try a Kinesis Advantage because I don't know anybody that owns one.
I now have two Microsoft Sculpt Ergonomic keyboards, one at home and one at work. And I love them. I didn't even realize that normal keyboards were causing me pain until I had to switch back to my old Das temporarily for a day and the whole of both of my forearms were on fire at the end of it. But in spite of all that, I still really really miss the Cherry MX Blue switches from my old Das Keyboard.
My point is that my dream keyboard, ignoring whether or not it's possible/feasible, would be a split-wave Microsoft-style ergonomic form factor with Cherry switches. If somebody out there put up a kickstarter for a keyboard like that tomorrow, I would empty my wallet backing the project. Maybe the Das Keyboard folks are here reading this.
A boy can dream.
They are currently in prototyping phase and they expect to go to Kickstarter this summer. I'm not from their team, I only want a good keyboard and this one looks promising.
I also own a Das Keyboard and I absolutely love the feel. But this "traditional" layout is just not good enough for today's typing-intensive professions. I have already experienced first RSI symptoms on both of my pinkies, so I'd like to try a true ergonomic keyboard.
You would empty your wallet backing a Kickstarter project but you won't spend a couple hundred dollars on a Kinesis Advantage? I don't understand.
I have two Kinesis Advantages and I plan to buy another when the new version is released.
If I tried a Kinesis and liked it, then yes I would buy it in a heart beat.
The only reason I'm using a full sized Das instead of a Filco tenkeyless is simply that the latter are harder to find in the US. In my case, my employer only orders office supplies through certain retailers which limits my selection.
I never use the number pad, and wish more manufacturers would offer tenkeyless models.
(This is one reason that Emacs and Vim are incredible editors and tiling window managers absolutely rock. There's basically never a need to touch the mouse unless your stupid window manager has decided to defocus the window.)
Btw, I don't think the mouse is altogether useless, but I tend to regard it as a last resort. If only we could actually mandate UIs which required that all functionality could be accessed via the keyboard (and have it actually work). One can dream...
The Happy Hacking Keyboard Pro (https://elitekeyboards.com/products.php?sub=pfu_keyboards,hh...) is probably the ultimate geek keyboard, and it's a reduced layout mechanical KB.
[EDIT:] I was wrong. Tore open my mac keyboard, and it's still a membrane switch, just one with good scissor workings to remove a number of the downsides of membrane switches.
Even for the claim of slimmest cherry switch keyboards, I believe they'll end up fighting against Corsair  over that right.
Then you can just pull the keycaps off and put them where ever you like. Aftermarket key caps are big among mechanical keyboard enthusiasts, and so almost all allow you to pull off the keys and arrange them how you want.
That said, most keyboards have slightly different slopes on the different rows, so if a key goes into the wrong row it'll feel wrong, so it may be a good idea to go for the Das Ultimate, with blank keycaps, or any other mechanical and buy a set of blank key caps, they're about 30 dollars.
Edit: It really depends on the switches, as well. Cherry MX greens, for example, have a much higher actuating force which some people find unpleasant even after long-term use. Browns and reds have a lower actuating force and are much nicer as a sort of "introduction" to mechanical keyboards.
I've been using the Logitech K750 which is wireless and a pleasure to type on (very soft). It also gets charged from any light source, so you don't have to think about replacing batteries.
You might also look at a Matias Quiet Pro - they use custom switches based off old Alps designs (much more satisfying than Cherries, imo) and are a fair bit quieter out of the box: http://matias.ca/quietpro/
Blues are a different story. Personally, I can't even stand hearing myself type with blues, let alone someone else. If someone had the balls to bring one of those into an open office I would probably need noise cancelling headphones to work in the same space.
As others have mentioned, the noise from brown mechanical switches is from the plastic bottoming out and not the switches themselves. Therefore, some keyboards are de-facto louder than others.
My Das, for instance, is definitely more audible than my backlit gaming Max keyboard. Both use the same brown key switches, but the plastic & keyboard construction is different resulting in a more muted typing experience with the latter.
IOW, I don't think brown keys are unreasonable for shared work environments; they're not much louder than a standard Dell rubber-domed KB.
The blue switches in my DasKeyboard at home however... I think I'll have to upgrade just to get something a bit quieter.
Brown - Same actuation point up and down. Has a tactile bump at the actuation point, but no audible click. Not as strong of a tactile sensation, since there's no moving piece to spring around on the key while traveling.
About halfway down, this page illustrates the different key types and how they work mechanically:
There's plenty of youtube vids comparing the two, I think this one  shows the difference quite well. Both blues and browns feel very similar, but the blues are much louder. Browns are already quite loud, and IMO blues are too loud - especially if you're in the same room as others. I went for browns.
Once you've typed on this thing for some time, there is no going back though (except, maybe MacBook keyboards, which are also superb)