Please note as of 12/7/2012 we strongly urge users to re-flash to Raring 13.04
The wiki also points users with problems to ask questions here:
This is leading to an influx in 13.04 Nexus 7 installation questions (though we haven't had too many yet).
Do we support 13.04 when it's being installed on a Nexus 7? We might me able to if we have enough users tinkering with Ubuntu on a Nexus 7.
There was a conversation about this in chat a while back, but I can't find it now.
If we don't support 13.04 on the Nexus 7 we will need to clarify that. Either in our FAQ or the Ubuntu wiki.