My wife's Titanium PowerBook G4 (667 MHz) is 7.5" from the left edge of the A key to the right edge of the semicolon key. It's actually a tiny bit bigger than the distance on my clicky IBM desktop keyboard. My Thinkpad T41 laptop is also 7.5". All 3 of these keyboards are 3.75" from the top of the number keys to the bottom of the space bar.
The Function keys and the arrow keys on the PB G4 and the T41 are smaller than on the desktop keyboard, but are roughly the same. I think that's ubiquitous on just about any laptop. The overall G4 keyboard width (left edge of Caps Lock to Right Edge of Enter) is 10-13/16" while it's 11-1/4" on the T41 and 11" on the clicky IBM keyboard.
I find it hard to believe that Apple's MacBook Pro or MacBook machines are more than a mm or so different from the PB G4. In what way is/was the PowerBook key spacing too small for you?
I think you need to do some measuring. :-)
Cheers,
Scott.