Set my address book to sync to one book in GW, that all went ok and the
device shows that GW book's contacts.

Changed my sync'ed address book in to GW to a different book, nothing seems
to happen. I would expect the contacts on the device from the old GW book
to disappear and the contacts from new GW book to appear but it hasn't
(after making the change about 3 hours ago).

I'm not seeing the changes reflected on the device, does it take a little
time for the changes to happen?