The sync that Google offers for Google Contacts <> Mac OS X Address Book is seriously flawed. It doesn't sync automatically, it doesn't sync all contacts, it doesn't sync all fields. See here for a list of warnings and issues.
Is there a better way to sync Google Contacts to Mac Address Book bidirectionally? Preferably free, and preferably without adding extra software.
I have tried to do it through Plaxo (which has an excellent Mac Address Book sync, albeit through an extra software install), but Plaxo doesn't handle Google Sync well (no updates).
UPDATE: For the new Mac OS X Snow Leopard this shouldn't be an issue. This question is looking for a Leopard answer.
Best Answer
Honestly, just hang in there until Snow Leopard, and its Exchange support for Address Book. Until then, just try to only add information through http://google.com/contacts, and perform a manual sync to pull the updates back to address book.
And make sure you regularly backup your address book and your google contacts, I've had one or the other blown away before by the sync utility on a rampage.