Also how does this affect SSL certificiate "pinning" as implemented in Chrome? I guess it doesn't since even if you have a pinned cert for a specific domain Chrome will still verify the trustworthiness of the CA that signed it?
TACK is just a proposed standard right now; I have no idea where it's going. But it's a good band-aid on the existing CA system.
Second, the protocol and the code need to be independently reviewed. This hasn't happened as of yet, but I am sure will if the popularity of Convergence increases. I'd be willing to give it a go at some point.
Third, we need a good-enough infrastructure to start with. SSL Labs (which I run at Qualys) sponsors Convergence by providing 4 notary servers (2 in the US, 2 in Europe). These notaries are installed by default, so you could say that the infrastructure is decent (at the current level of usage).
Finally, we need to have the technology available in all major browsers, at the very least pre-installed and available as an option, but -- ideally -- fully integrated ("This looks like a self-signed certificate; please wait for a moment while we verify that you are not under an attack"). A big problem for adoption is that browsers are lacking APIs for this type of work.
[kinda frustrating that the solution to many of these issues is sitting here at the bottom of the thread!]