My big problem with BitComet (which is my current preferred client) is that I can't even APPROACH my upstream maximum without saturating my connection to the point of completely fruiting out my modem.
I use Comcast, and have 4.5Mbit down and "384K" up. I can, on a single upload, get about 512Kbit uploads.
However, Bit Torrent involves so damn many ACK packets that I can't even routinely get past 25KB (as opposed to 50 or more) without saturating the connection and making the network unusable.
Bit Comet's solution to this is to set a "per torrent" connection limit, but it'd take a boatload of fiddling to determine what the total connection limit is. I'd much rather use a client with an "anti-freeze" option that senses network slowdown and desaturates... which is what BitSpirit seems to do.
I'll try it out and let you know, but it looks promising.
I'm perpetually irked that P2P programs, despite being used PRIMARILY by people with Cable modems and DSL, don't really seem to have been designed with cable modems and DSL modems in mind! MOST cable systems in the USA have 3mbit/256 or 3mbit/384 connections, but you will NEVER see that as an option on one of these programs. Most DSL is 768K/128K or 1.5Mbit/256K, but that's never an option either.
And virtually ALL cable/DSL have a packet cap - meaning that no matter what the total maximum throughput is, there's a substantive limit on the number of packets that can be put through, regardless of size. And NO P2P program really takes this into consideration. It's as though they're all written by and for people on T3's.