MS Encarta
I've seen all three — Encarta, Compton's, and Grolliers (not the Windows
version). Here are my thoughts.
Encarta is super. Love it. but it's not ready yet; only saw it in alpha.
Compton's is jazzy, but neither I nor my family find it easy to use. The
kids don't find it really helps them with their homework all that well.
Grolliers has been solid. It has the information, and it is very
accessible. Gets the most use.
Hope that helps.
Ron