As a user, I was personally a little frustrated trying to figure out
a few migration aspects. The 5.1 manual highlights incompatibilities
between 5.1 and 5.0, but doesn't explain how to overcome them.
I am afraid it is too late to fix this in the manual (5.1 is already
out). Maybe someone could volunteer to write a page in the wiki with
this material? It would be really useful. (Actually, I think the wiki
is a better place than the manual for this kind of material. As you
said, some changes are almost automatic, but others may offer different
alternatives involving specific techniques for specific situations.)
-- Roberto