I happen to have shields for both the fez and arduino. The one BIG problem with the fez shields is that the legs that stack the shields together are to short. For example, if I stack the ethernet shield and lcd shield, they actually touch, and do not fit. But, the legs on the real arduino shields are longer, and I can stack those shields with no component touching.
Another example, if I stack the serial shield on the fez, and then put the ethernet shield on top of the serial shield, the db9 connector on the serial shield touches the connections on the ethernet shield!!!
Follow what the arduino shields do and extent the legs just a tad so the shields do not touch!