Slow , yes it can be. I need to be carefull .. I'm not using strings at all (very slow in VB) .. and treating all network traffic as byte arrays which helps a lot ! ... I have no problem mataining 7 peers on my ADSL line with <10% cpu ...
Running it all on one thread is a little tricky too, I'm currently running it on VB6 .. hopefully once I move up to VB.NET I can have seperate threads for peers/upload/downloads

Joe