The more peers, the better the odds (obviously) of faster downloads.
The saying goes that the faster you can upload, the faster you can download as well. Personally, I never allow more than 8k upload per torrent (I can get around 28k max upload), but have downloaded torrents in excess of 180k.
But if you're going to use torrents, please don't be a leech and make sure you get a download/upload ratio of 1:1 (meaning, you download 100meg, you also upload 100meg) before stopping the torrent.