It is not about how many devices, it is about how many subnets, because you may want to keep them isolated, for many reasons.
It is not just about devices consuming lots of bandwidth, it is also about many small sensors, actuators and so.
I have no problems with giving the customer several subnets. /56 is just fine for that. I haven't seen any kind of realistic scenarios which require /48 for residential users *and* will actually use lots and lots of subnets - without requiring a similar amount of manual configuration on the part of the customer. So we end up with /56 for residential users.
And I'm not saying to forget about what we have learn with DHCP, in fact DHCPv6 has many new and good features, but for many reasons, autonconfiguration is good enough, and much more simple.
For our scenarios DHCPv6 is needed, autoconfiguration is *not* good enough. It seems quite likely that in many cases the CPE will use the /56 it gets from us (via DHCPv6 PD) as basis for autoconfiguration on the LAN side - and that's just fine and dandy. [I see no point in repeating the arguments for why autoconfiguration is not good enough - this has been beaten to death, repeatedly, on lots of IPv6 lists.] Steinar Haug, Nethelp consulting, sthaug@nethelp.no