I share this in the hopes that it saves someone else a bit of grief, or at the very least, offers a solution to a fairly common problem with the Eris and wireless contact sync.
My contacts were copied from my Blackberry Curve (which had been sync'ed to my Outlook contacts) to the Eris at the Verizon store. They sync'ed with my Google contacts fine at first - I could see all of the new contacts in my GMail contacts - but I couldn't get full wireless sync. Specifically, I could not get new contacts I put into the phone to show up in my Gmail contacts. I kept getting error messages on the device about the service being unavailable.
Unfortunately, the easiest and surest solution was to do a hard reset on the Eris and start from scratch. Since then, all of my contacts show up as "Google," not "phone," and I have full two-way wireless syncing.
I kept hoping for a solution less dramatic than the hard reset, but found none. This seems to be the best, if not the only, way to go.
Thankfully, I had yet to overly-personalize the phone and hadn't purchased any apps, so nothing lost there.