Thanks. An initial list of errata will appear this weekend (probably tomorrow). I think I'll add a RSS feed for it :)
W.r.t. actors and scheme: the whole thing is that Sussman and Steele started Scheme to figure out actors, did some hacking to do async stuff on top of Maclisp, essentially, and then found out that their stuff and (Hewitt-style) actors were the same. So I guess Scheme took "the same but a different" path early on, pretty much how Erlang and Golang are pretty much similarly powerful systems, expressing the same functionality in different ways.
W.r.t. actors and scheme: the whole thing is that Sussman and Steele started Scheme to figure out actors, did some hacking to do async stuff on top of Maclisp, essentially, and then found out that their stuff and (Hewitt-style) actors were the same. So I guess Scheme took "the same but a different" path early on, pretty much how Erlang and Golang are pretty much similarly powerful systems, expressing the same functionality in different ways.