[U2Lynne]

Well, since you were firewalled before, that means that you couldn't connect to everyone on the torrent and therefore your speed was not as great as it could have been. Once you are no longer firewalled, you are able to connect to everyone. When you are firewalled, not everyone can 'see' you and therefore they can't download to you.

You should be fine security-wise unless there is some vulnerability in your bittorrent client (and I have never heard of this being the case).