I can concur that 12.0.1 seems to have fixed this for me as well -- it's a
dramatic improvement.
I had put away Entourage 2004 last year since it was dog-slow under Rosetta,
and went back to Mail/iCal. When Entourage 2008 came out I grabbed a copy
right away and started converting everything over to it. The Sync Services
situation was SO bad, however, that my Entourage 12.0.0 experience lasted
for about a day before I threw up my hands in disgust and decided to go back
to Mail/iCal until the next update.
When 12.0.1 became available, I pounced on it in hopes that it would fix
these issues, and for the most part it seems to have done so. I had a few
duplicated contacts in Entourage after my first sync, but I merely cleaned
them out manually, and it's been syncing back and forth fine ever since.
Note that there still appears to be a problem actually *applying* the 12.0.1
update for Entourage itself. Even if you've downloaded the latest version
and applied it, be sure you check your "About" screen and confirm that it's
actually showing 12.0.1, otherwise you're still at least partially running
the older (broken) version.
If you find yourself in this issue, you can fix it by following the
instructions at
http://blog.entourage.mvps.org/2008/03/entourage_still_states_1200.html#more
Either do a full remove, reinstall, reupdate as suggested in the main
article, which is the best (although most cumbersome) solution, or look at
my comment to the post for a faster workaround to update *just* the
Entourage components that seems to have worked out just fine for me.