It is not BitTorrent (the protocol) or the particular client software that are slow, it's just the particular torrent you're trying to receive or, more precisely, the hosts which make it available at the moment, the available or allocated bandwidth they provide and the competition from other receiving BitTorrent clients for that torrent.
I've seen very high throughputs (up to the limit of my 6 megabit-per-second inbound DSL link).
I have no problems with BitTorrent speeds. I use Azureus, and I've setup port forwarding on my firewall for the ports that Azureus wants to use. I have a 12Mbit BB connection ot the internet, and I regularly see my BitTorrents coming in at a combined speed of 600K/s to 800K/s and even sometimes higher. As was pointed out, your Bit Torrent speeds really depend on several factors, including how many complete copies are available of the file(s) you are downloading. In some cases, BitTorrent is easily faster than what any FTP site can give me... in other cases, the FTP option is a better choice. C.