I recently found that the horrible lags I was experiencing while browsing sites were caused by uTorrent. There's was no upload/download activity, just updating trackers and finding peers to seed. utorrent worked just fine but not my internet browser, which spent a couple (5-10) seconds before sending each request according to Fiddler.
I keep around 40 torrents, the settings are (I've got them from azureus bot):
global max number of connections : 500
max number of peers per torrent: 144
max upload slots per torrent: 8
use additional upload slots if speed < 90% : true
What are the correct settings for my 8Mbit/8Mbit line? OS is WinXP SP3 if it has any relevance.