Hi Rob-
I ran into this myself not knowing what to do, but being a mostly Microsoft shop we installed Windows Server 2008 R2 Datacenter, created a service account and added the account to the local admin users group. Then I turned off the UAC and installed Office 2010 w/ SP1 64-bit before I ran the preview server installer from the data-va. After it runs it creates two accounts, one of which it unfortunately has to be logged in with at all times for it to work. We left the machine locked and that was it. It previews word docs alright with nothing else but the above but it is VERY slow to render.
I did notice that if your machine didn't trust the Internal Root CA from the gateway nothing would display. If you're using the FQDN to one of the connectors used without kerberos it seems to work better but still slow.
Hope this helps.