After six weeks of shooting and shooting and shooting trying to make sense of what I was experiencing with my XTi... and listening to many tell me that I haven't got a bloody clue, and that I should go back to film, and that I should learn to "see" (not just on MM, but other forums as well), I finally met with a Canon rep (in person) and he tells me... I'm right... there's something wrong with my camera. He quickly has the store replace it with another new XTi and I leave. After two days of shooting... I can assure you, the new camera is performing as I would expect. All exposure issues are gone!

Listen to me people... if you own an XTi, that you paid a chunk of change for, and it's underexposing... then get it checked while it's under warranty. Cameras should expose properly... period. Cameras that have an "Auto" mode should work as a point & shoot... period. Do NOT listen to anyone that tells you different.

This will be my last post on this particular issue. Now that I have a properly working XTi, I'm a happy camper.

Oh, and does my new XTi underexpose?  Yes... by about 0.5 stops on average; but nothing like the 1 to 1.5 stops of the previous camera.