Why are so few of the first 550 preorders currently set on the 4GB version of the Pyra variants? Isn't that a high risk as it's not yet been tested and that it could EAT so much into the Pyra's battery life (for each battery I know)? Did you know that the RAM and CPU are on the same socket so that if you need more RAM you could upgrade to a newer CPU with a bigger RAM amount in the future?
I'm assuming that RAM refresh is only a tiny fraction of the power consumption. It should be insignificant for the usage time (i.e. when the screen is also powered, which will consumes orders of magnitude more power). It will have an influence on lid-closed standby time, but if that's too big of an issue, we can always implement suspend-to-disk to improve the standby time.
Also I'm assuming that it might be possible to disable half the RAM in software (at boot time or something) and switch it off completely, effectively turning the 4GB unit into a 2GB unit for all practical purposes.
Finally, I think that if the choice is between 2x1GB chips or 4x1GB chips, then it might be the case (but I don't know enough about this to be sure) that 4GB units will not just have more RAM, but also faster RAM since the half-filled configuration (2GB) might take less advantage of the available memory bandwidth.
So taking all these things into consideration, plus the relatively small price difference between the two options (only 5% extra), I think 4GB of RAM makes sense. While I don't think I'll really need the extra RAM, it never hurts. I think RAM is most likely to become the first performance bottleneck as the device ages, especially if we're going to use software that's intended for desktop/server hardware where RAM is usually available in generous quantities.