If you're using a router, you HAVE to make sure your ports are forwarded properly, or you will spend weeks dl'ing shit. Dunno how to, just msg me.
In a large swarm, this simply isn't true. You will be able to connect to enough non-firewalled peers that your speeds will be fine. If there is a small number of peers, yes, forwarding your BT port so you aren't firewalled will allow you to maximize your connections and get the best speeds you can. That being said, you can only download as fast as the other peers are uploading. If they have 20 torrents open, you are only going to get it in dribs and drabs. YMMV and probably does.