Get it out of your head right now that you can just download to the max and cap your upload, to get the file faster and then pay back the torrent when you have got it. The principals of how BT works is that a file is broken into pieces, the uploader sends these pieces out, in linear order or if in superseed mode, where needed (never superseed, just causes too many problems!) If you have four peers and one uploader, with the uploader setting their client to connect to four peers, each peer will receive a different piece, most likely in order, peer one statistically will receive pieces 1, 5, 9, 13, 17. This means that whilst downloading the pieces of the torrent off the uploader, you want to be downloading the pieces already given out by the uploader, and in turn, those peers want every other peers pieces.
I am going to describe two broadband lines and average speeds you will see, and beginner with one of these two lines has it easy now. 512/256 you can download at 50/51kbs whilst uploading 20kbs at the same time 1Meg/256 you can download about 100/102 whilst uploading 20kbs at the same time.
Are you bored waiting and go start another smaller torrent while you are waiting (that won't work, now your upload speed is divided between two torrents, making the problem worse!)
Has the uploader decided that with their fantastic foreign line that they will upload 4 DVD's worth of data at the same time? Are you starting to panic, thinking that with your line, by the time you get the first torrent, and pay back, the next torrent won't be working anymore?
So, what are you going to do? Jump on all 4 torrents? Give an average upload speed of 5kbs to each torrent? Not care about damaging the speeds of the torrents, because "cool torrent mate! I'll keep my client open for weeks to keep this beauty alive!" yeah, well at 5kbs you will need weeks to pay all the torrents back.
This is where everyone has to understand a very simple fact about torrents, that sadly many people are choosing to ignore. By not uploading the pieces you received from the uploader, YOU are damaging the torrent. YOU are doing it, it's YOUR fault. Patterns emerge, people ban your IP in their client, days, weeks, months from now the IP's have been exchanged between uploaders and stuck in trackers. there comes a time when your speeds go to hell, you can't get data off people, everything's so slow you start to bitch and whine about the speeds, without comprehending that maybe your actions in the first place caused this. That IP might even get shared with BT sites where I know people can enter the IP in their tracker and who in turn trust me to make educated decisions and not be juvenile about this sort of thing.
So, everybody think about the health of torrents. DON'T cap your upload and DON'T try and get too many torrents at once.
Think carefully and pass the word, the information and reasoning on how to properly maintain a torrent needs to be in everyone's minds and acted upon.