FWIW, my GoPiGo SD card shipped with a blank hostname. This breaks bonjour.
`pi@(none) ~ $ ls -l /etc/hostname
-rw-r–r-- 1 root root 0 Nov 10 11:54 /etc/hostname
Setting the hostname (instructions here: http://www.dexterindustries.com/howto/change-the-hostname-of-your-pi/) got my bon jour working correctly. I recommend at least checking to make sure your hostname is set.
UPDATE: Even after getting bon jour working I still couldn’t get vnc working (specifically NoVNC, connecting directyl with a VNC client worked fine), so I ended up pulling down the latest “Robots for Raspberry” image (see: http://www.dexterindustries.com/howto/install-raspbian-for-robots-image-on-an-sd-card/) and installed it. I wish I had captured the version I was running before I re-imaged the card. The downloaded version seems to working well; hostname was set and novnc worked fine.