stream -> file: slow? don't forget you're using a scripting language..
file -> stream: some have suggested before that "on SOCKWRITE" should be triggered whenever mIRC has sent some of the data, instead of all of it. That would take care of the problem here.
stream -> stream: it would be nice if mIRC used its own buffering for outgoing data, instead of relying on the fixed-size buffer that winsock provides.
The things you suggest are way too specific for my liking at least..
