I don't think you want the serverQueue.length check here.  If we were going to process a server op its branch of the chained-ifs would have stolen control flow and we wouldn't be in the "else if" case.  (NB: I have this change in my streaming patch too, and that's how I did it there.)

Also, unless you feel strongly about the comment right here, I'd remove it just because I have that same hunk sans comment and then my rebase will be less painful and I think this.  Your call; I think the code reads relatively clear here, but since you are the person who was probably going 'WTF' a bit, you'd know better how much the comment is needed.  If you do want one, maybe move it to the head of the if chain and have it be something like "Run the next operation if we can, otherwise generate a completion notification."