I have two of those IBM Model M keyboards. They use more power than modern computers can supply, which is why the great upgrade project of 2007 failed (only I didn't know that at the time). But they are, simply put, the best keyboards I've ever owned, and I fully intend to have one of them buried with me when the time comes. (I got them for free, used. How do you like that?)
Marko's answer was to buy a new and spendy one, but as a best-selling author he has more resources than I do. I'm used to the keyboard that came with Cephiro, so I've continued to use that one with Floristica. It has full-stroke keys, though they are membrane type, and the keycap spacing is perfect for touch-typing.
I've used a crapton of keyboards over the years, and some were better than others.
The worst was the Atari 520 ST keyboard. Holy crap did that suck; the keys were too close together and they didn't have a good stroke, and touch-typing was harder than it should have been.
The C-64 keyboard was pretty good, but for a few deficits. The biggest was the height of the thing; since the keyboard was essentially atop the motherboard it made for a too-high wrist angle when the hands were properly suspended over the keyboard. This way lies RSI and carpal tunnel. The other deficit was that it gummed up very easily: even though I didn't eat over it, I periodically had to disassemble it--desoldering the caps lock button to get the circuit board off--and clean the contacts with alcohol. It wasn't food or liquid, but simple dust contamination that made it flaky. Otherwise, it was a good full-stroke keyboard with excellent keycap spacing.
I have consistently eschewed any "chiclet" keyboards. They're fine for casual use, but not for serious writing.
The IBM Model M was the best. The Microsoft Natural I used for a while was pretty good, but it's hard to make the switch to-and-from a flat keyboard to a split, curved one, and I've found that my wrists don't need an ergonomic keyboard, regardless of how much I write.
I never used the Amiga 500 (bought used from a friend) enough to really decide how I liked its keyboard. Ditto for the Macintosh SE, and the TRS-80 Model I that I hacked around on during the summer of 1991.
The NEC MultiSpeed had a good keyboard. Once I had the Model M, though, I used it exclusively, until I had to use an MS Natural for work; and after that died, I went back to the M until I could no longer use it.
Now, at work they have a gamer's keyboard that has the nice clicky keys, full-travel, with the right spacing, and it's a snip at $150...why, I'll buy two!