My upgrade experience
Super easy with TWC. I noticed on my bill I had been upgraded to 300/20 but my modem was only rated for 100/5. I went in, they gave me a new box and blammo! 320/22 with a wired connection. 320/22 via my Airport Extreme to a rMBP. Yeah. I'm loving life right now.
BUT... my issue is with the NAT infrastructure between the two. I normally like to have the DHCP server on the AE in case something happens to the Cable Modem (service goes out, cable modem dies, etc.). This will allow me to have limited functionality in the house (NAS, TiVo streaming, etc.). I haven't quite figured out how to get bridging to properly work between the two. The Arris has a setting to disable DHCP assignment and enable bridge mode. I can then successfully get DHCP / NAT working properly on the AE. However, I lose access to the web gui on the Arris. I've tried giving the Arris a dedicated IP on the subnet for the AE but it's been a no-go. Also, the Arris web gui can be quite slow when there are many clients on the device. Response to a webpage on the Arris can take up to 10 minutes to render! This makes trial and error quite difficult (not including the reboot times)
I just got the link to the Arris Web Gui manual so I'll take a breeze through that and report back to the forums. For now, I'm using the Arris DHCP server.