I wish the big browser makers would implement this, but only for IPv6 and non-NAT IPv4, because of the problems that crappy NAT translators cause for SCTP.
Aside from the performance improvement to be had in certain cases, I would really like the multihomed-ness support that can be set up with TCP, so that a device with both a wireless LAN connection and a 4G connection simultaneously available could switch from one service to another seamlessly without the breakage that happens with TCP when a client decide changes its own IP when it moves from one network to another.
I could use this to make the 3G/4G failover feature of my Firebrick FB2700 work properly, i.e. seamlessly, but only if Andrews and Arnold get IPv6 going over 3G/4G.