You can always see what has happened between two changesets (tags or otherwise) simply by passing the revision range to the appropriate log or diff command.
To see all of the changesets that were introduced between, say, the tags
hg log -r v1.0:v1.1
To see the net sum of differences introduced in those revisions, you'd instead run:
hg diff -r v1.0:v1.1
If you are curious simply of everything that was introduced since the last tag (assuming the last tag was
v1.0), simply substitute the word
tip for the second tag. E.g.:
hg log -r v1.0:tip
will show you everything you've done since 1.0.
Mercurial can even format this output in changelog-style, if you want. Simply add the
--style changelog parameter:
hg log -r v1.0:v1.1 --style changelog