The streaming problem on Be is apparently down to iPlayer! (The extra traffic via Akamai was enough to choke up Be's Akamai link; they're working on upgrading it, but for some reason it's taking a long time.)
NAT traversal is really only an issue when both ends are NATted; most games would be communicating with a central server, which avoids that problem entirely. Pure peer to peer setups like Skype and BitTorrent will benefit, although with most routers supporting UPnP these days that's a fairly minor problem - any peer to peer application can open a listening socket for the outside world quite easily anyway.
Behind an elderly (pre-UPnP) router or a jackbooted firewall it's a problem (Dundee University blocks inbound connections, not because of NAT but plain old firewall rules) but neither of those will be changed by IPv6 any time soon anyway.
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NAT traversal is really only an issue when both ends are NATted; most games would be communicating with a central server, which avoids that problem entirely. Pure peer to peer setups like Skype and BitTorrent will benefit, although with most routers supporting UPnP these days that's a fairly minor problem - any peer to peer application can open a listening socket for the outside world quite easily anyway.
Behind an elderly (pre-UPnP) router or a jackbooted firewall it's a problem (Dundee University blocks inbound connections, not because of NAT but plain old firewall rules) but neither of those will be changed by IPv6 any time soon anyway.