[brudgers]

For me, symmetric C- and M- provides a good layout because I can use either hand for C- or M- and the other for the additional keypress. Having one on either side of the spacebar but asymmetricly located is ok, but not as good.

I have found that having only one C- key on the keyboard becomes uncomfortable over time. For example C-a and C-e and C-x and C-f contort my hand more with only a left hand C- key...looking for this in a keyboard is one of the things I learned from Xah's site.