My type of photography is outdoor wilderness landscape photography. I have not really paid much attention to the type of lighting conditions in which I prefer the +1/3 frame over the metered frame, but maybe I should go through some of my slides and take note. I also admit that if you just shoot it at its rated 50 that the slides look very good as well. However, sometimes when I have three frames side by side (ISO 40,50,64), I prefer the +1/3 frame.
"Canon's EOS Evaluative meters (right back to the EOS 1N, which is my weapon of choice) can be considered extremely accurate, but partial and spot metering on Velvia in difficult light are also exceptionally useful."
I use the spot meter quite a bit when shooting extremely contrasty scenes, and find it quite accurate if you know where to place certain tones around middle-tone. However, if the dynamic range of the scene will fall within what Velvia can handle, then Nikon's or Canon's multi-pattern meters do indeed deliver perfect results.