Denis Germain , May 20, 2007; 11:56 p.m.
The XTI is NOT a semi-pro camera in Canon's world... but it works fine in extreme environments (except heavy rain - but a good ziplock and a piece of tape can do wonders for this).
The plastic build or the better build found in a 30D, 5D or D200 will not Seal your camera against dust, sand and moisture.
Be careful and don't change lense in the middle of the desert. and perhaps, buy a second body to avoid lens changes.