You can also use www.nuevasync.com who also provide an Exchange interface to Google Calendar and Contacts. They deliberately filter out Google's suggested contacts.

I haven't actually used the contact side of it yet, but the calendar sync works well.

Dragging up an old thread:

I just tried the iPhone ActiveSync support with Google. For my contacts, where I had previously kept a careful list of them in Apple's Address Book and allowed Gmail's contacts to run wild, the result was a mess. For contacts that existed only in my Address Book, they showed up without too much mess at Google. For contacts which exist in both, no phone numbers actually migrated to Google. Had I continued with the active contact sync business, I could well have lost all my phone numbers -- clearly unacceptable.

Luckily, I backed everything up, so restoring my Address Book contents did the right thing. Not having that actively synced with Google isn't really the end of the world for me.

Calendars are another matter. Google is the primary source of my calendar. I configured the "Exchange" synchronization for calendars only, and that seems to work quite well. The only issue, sadly, is that the calendar *colors* don't come through properly from Google Calendar. See, for example, this thread. There seems to be no good way to solve this problem, save jailbreaking your phone and editing a color in a SQLite database.

I haven't attempted any contact syncing for just this reason. I am really waiting until there is still a good solution that will allow Eyrl and I to share synced contacts like we can with shared sync Google calendars.

When I had Exchange syncing to my phone, the contacts were separate from my personal contacts. Though I do use MobileMe, so it may only separate when you have multiple push services, vs syncing via the dock.