First <i>branded</i> phone on T-Mobile with IPv6.<p>Also, the HTC One S has been available on T-Mo for a few days now; it's running ICS and should thus support IPv6. Wouldn't that make it the first branded IPv6-capable phone?<p>Edit: As noted below, the software on the One S does indeed not support IPv6 as of now.
I don't see how IPv6 on mobile data helps anyone but law enforcement and your mobile provider. Keeping smartphones behind a NAT (that can still speak IPv6 to the outside world if it were inclined to do so) and avoiding the baseband turmoil seems like a winning strategy.