I'm in the same boat as you are.. Exactly the same upgrade, service calls, tech responses.. Such a bs! On my old 300mb connection I used to get upto 500! Same tap, cables and end devices. I can't imagine how the would sell and upgrade to gig and down...
Current Firmware: 2.0.10.36T6
Guest WiFi - Gives 'only allow DHCP client to use this wireless'
I assume that I am already at the latest firmware. Any fix would be much appreciated.