I think having the number keys as on _wb_'s proposal is good, as space is saved. (F)(1-0).
I am in favour of having ESC on the leftmost button on the topmost row because:
1 - It is unlikely, then, to be pressed accidentally,
2 - I think it would be easier to deal with, as a VIM user, than Fn+TAB, and Fn+Q, where Q is not a corner/edge key, is HORRIBLE,
3 - I think it is not too difficult to reach, assuming it is similar to the number 4 on the Pandora: having tested it, I find it no worse than the ESC on the normal QWERTY keyboard, for frequent VIM use,
4 - I think it would be easy to find, as there would be no keys to its left, as on a Pandora.
Lid-close as a special (super) key for media keys is nice, especially if it also counts for the Pyra/super key: it would allow the use of certain Music Player Daemon applets, which accept the media key commands without being the main application with focus (there is a decent one in xfce4-goodies, I believe). EDIT: here it is:
http://goodies.xfce.org/projects/panel-plugins/xfce4-mpc-plugin
If there are worries about backspace being pressed accidentally, I propose rightmost topmost as a decent place, like the 8 on the Pandora. I think it would be easy to reach and to find, as there are no keys to its right.
I am not particularly keen to devise my own layout just to showcase all of these -- would doing so make my arguments more convincing?