A lot of people have commented on various topics about the extreme slowdown of Internet surfing while downloading using the various bit torrent softwares available. I too experience this (thought to be) issue and have a simple solution.
Peer/Seed connection and max download/upload speed is essential for downloading at the quickest possible time/speed. If, however, you still browse the internet while downloading then the max settings should NOT be used. This will utilize ALL available resources for downloading/uploading for 1 piece of software. It is best to allow 10% for browsing (in my case browsing this forum), this means that instead of max upload/download you use 90% of each (e.g. if you download @ 1MB/s then set your software to 900Kb/s, and an upload of 100Kb/s to 90Kb/s).
This will reduce the download speed of you torrent(s) but will greatly increase browser speed.
I would also recommend changing the 'Maximum Global Connections' to 1000+ & 'Max Connected Peers per torrent' to 250+ . This will greatly increase the chance of connecting to Peers & overall download speed will increase (this is for the benefit of those who experience slow downloding of torrents). The exact terminology of these setting may be different as i'm using µtorrent as and example software.
Hope this little infothread helps