For me, it's been keyboards with ctl and alt on both sides. Thanks to Xah Lee [1]. This rules out Macbooks (and most laptops) and favors Thinkpads, though currently I have a Dell Precision laptop and it has ctl and alt on both sides but the ctl's are not symmetrically placed and it is a bit annoying and not as good as the Thinkpad it replaced but it is workable.
On my desktop, I have a Microsoft Natural Ergonomic 4000, which is an awesome keyboard and cheap and robust. The major compromise is that it is corded to USB, but for me it is worth it.
That said, it takes practice to develop muscle memory to use both ctl keys and both alts and key bindings that require switching ctl keys to touch type feel strange.
Good points. I also swap Ctrl and Alt on both sides, using my thumbs for Ctrl. Using the opposite hand to press the modifier is analogous to how a touch typist uses the shift keys. For desktop use, I now use a Kinesis keyboard, again with symmetrical modifiers but all as thumb keys.
On my desktop, I have a Microsoft Natural Ergonomic 4000, which is an awesome keyboard and cheap and robust. The major compromise is that it is corded to USB, but for me it is worth it.
That said, it takes practice to develop muscle memory to use both ctl keys and both alts and key bindings that require switching ctl keys to touch type feel strange.
[1]: http://ergoemacs.org/emacs/emacs_pinky.html