its works very well.. but just make sure you see the contacts added in gmail before doing the last step. The 1st phone i synced was easy as pie, so when i did my 2nd one i didnt double check the contact in google (for some reason this can catch a snag at this point) and when i went to sync them back to the iphone .. i had lost them all!!
A simple restore can fix that problem but just make sure you double check everything was sent to google.