Rob,
Honestly, how many shields have pass-thru headers? I count mine, and which else (I think one of the adafruit or sparkfun shields).
According to arduino team's product stock photo, none of their shields have pass-thru headers:
Here is mine:
http://www.inmojo.com/store/liudr-arduino-and-physics-gadgets/item/sdi-12-serial-logger-shield/
I might just bite the bullet and add SD card and xbee support stuff on this shield, going with surface mount ATMEGA328P-AU, and forget about stacking. At least for one project it will eliminate the official arduino wireless (xbee) shield.