I'd like to think that the Erlang has proven its value at building reliable, distributed applications. It's a go to language for distributed key value stores (Riak, Couch, et al), and it's in wide use in Motorola and Ericsson to build critical infrastructure. I call that successful.
That said, you do have a valid point: The presentation provides justifications for those that want to switch in the first place, but to be compelling, it needs evidence.
I work in Erlang and love it, but I would make the friendly argument that Erlang is really distinct (and special) even among the FP languages for a number of reasons. I always had the impression that Erlang was functional to support the guarantees made by the runtime rather than for ideological reasons. Some of the Functionistas I've run into seem to reject it out of hand for not being Haskell, but as a C guy I find it freaking amazing for writing stuff that has to stay running all the time. I guess I use in spite of it being functional rather than because of it, but it feels like I'm getting good value even when I run into things that are a pain in the ass to do functionally (which is not super often).
That said, you do have a valid point: The presentation provides justifications for those that want to switch in the first place, but to be compelling, it needs evidence.