Encrypted Bittorrent traffic is always going to be a problem. Try limiting the open ports to services you require, not a simple any rule.
This is a good practice regardless... you can avoid a lot of headaches by limiting your outgoing traffic to necessary ports / hosts. For example... outgoing SMTP should not be open to everyone unless necessary. If one machine gets a spambot on it you could have your IP blacklisted, seriously impeding your ability to send emails. If you set up your rules so only your mail server can access outgoing SMTP this would not happen. I know that from personal experience.
