Been trying to download the new firmware but all I'm getting on Mega is "Temporary error, retrying". Its been like that all evening even earlier when I were on a FON connection (a FON connection faster than my current ADSL as its someone on Infinity).
I have managed to get it working with the router doing the PPP connection. When configured for PPPoE port binding DOES work, it bridges eth0.5 (LAN1) to atm1_1, which is what you would expect to happen.
Apparently the key thing I missed that I REALLY didn't think would make any difference is encapsulation MUST be LLC, when set to VCMUX no traffic was passing over the bridge. I don't remember that being a stipulation on my old Netgear but its been a while.
A not so exhaustive test (traceroute) seems to imply it shaves 5ms off the latency having PPP done on my Atom rather than the HG612, but it could be coincidence.
Bottom line, with the HG612 doing the ppp, port binding seems to be broken. I also never managed to get plain routing working with the block of IPs either. Its not so bad as I was more thinking I was going to use them for multi-NAT/multi-DMZ anyway.
Interestingly, my connection started on G.DMT at around 4000/800 but after rebooting earlier it swapped to ADSL2+ at 3829/588 with my SNR looking dangerously low at 4.6/3 and falling. Bummer, I used to push 5500/1000 on Be, I guess crosstalk has really become an issue in the meantime.