I'd like a good answer on that one as well, specifically, the difference b/t Evaluative and Center W. Avg.

Thus far, on my XTi I can only tell a difference when I shoot partial, as it only meters for what's in the circle - say it's a shadow and there's a highlight in the corner, the highlight will be blown but the shadows won't be too dark. On the other hand, last weekend I went back and forth b/t CWA and Evaluative and couldn't tell one bit of difference b/t the two.

Spot is great, which I wish the XTi had. For spot, say you want to photograph a lit face in front of a very dark (night or heavy shadow) background. With spot, you can meter on the face only, whereas evaluative would try to balance b/t the face and the dark background, making the face too dark.

At least, that's my understanding thus far...