For me it was automatic, I had all my contacts on google, switched phones to this one, added my google acount to phone, and Bam- there they were.
2 problems I see with using google contacts-
1. google auto adds all addresses you email, including all craigslist emails and whatnot. So first time you sync, you may have to clean those out.
2. You cant change ringtones for google contacts-unless you put them on the "phone" contact list