Xsi over exposing?

I've seen a few posts that refer to the Xsi over exposing...this is hard to correct and would be a big issue in wedding pics.

Is this a regular problem? I found if anything the XT I have underexposed. Opinions appreciated!

Outdoors mine typically overexposes by 1/3 of a stop or less in Av mode. It's really easy to correct, you just take one picture and then slide the little exposure compensation bar one mark to the left if needed before taking any more pictures. If you shoot in RAW it doesn't really matter very much because there's more than enough data to fix it in post if needed.

That's what the EC dials are for, and M.

No metering system is perfect and they don't seem to be very consistent from model to model. You just have to learn the nuances of the new camera.