I have the exact same equipment as you do. You don't have to put the Ubee in bridge mode. Just set up the Airport Extreme so it is actually bridging from the Ubee via Ethernet out to Wi-Fi, and give it the same SSID, security, and passphrase settings as the Ubee. And you're good to go. I have no issues with this setup, and speed is just as good as it can be.
I recently upgraded to D3 and discovered I now have a tiny bit of packet loss (0.2%). I could go for 30 minutes without a dropped packet, speed tests were excellent but when you drop a packet in the middle of gaming you know it. Once I enabled bridge mode the packet loss vanished. BTW the packet loss was present when I only had one PC directly connected via ethernet so it wasn't the double NAT of daisy chained routers causing an issue. The built in router is just not very good - probably a software update would fix but I suppose that's between ubee and TWC to figure out.
I finally went ahead and bridged my Ubee because I wanted to have IPv6 on my home network and my Apple Airport Extreme handled it very nicely. Everything is still working fine. Bridging was easy for me, but requires some network knowledge and I don't recommend it for the average Joe or Jane customer.