A common misconception. I have it and don't have an iPhone. I do use iSync with a different mobile phone, though. And have used iTunes to sync contacts to an iPod. Not sure which enables the Google sync plug-in. But I've never used the "red-herring" hack.
If you do get this going, I suggest starting with no contacts at Google. Import any you don't have but want in Address Book first, backup your Address Book data, then wipe your Google contacts, then sync.
I've had it enabled for a few weeks and so far so good. I only have a few dozen contacts, so any irregularities are fairly easy to spot. Which I've only had a couple (partial dupes).
But again, do not start without backing up first.