There have been some improvements on Steam!
As tey wrote in their Newssection, they’ve highly increased their bandwidth and changed the content deliver system from some weird technology to our friend the http protocol.
That results in better downloading: for example if you are behind a firewall, it will more easily slip through port 80. You can already check out that speed by downloading trailer, as they have, at the moment, added the method for trailers only.
It gave me 130KB/s for a few secs, after that it went to my maximum capacity, pretty impressive.
Because of the system update, the patch publishishing for third party developers is much easier.
Some upcoming client updates will include download scheduling, bandwith throttling (!), prioritizing which games get downlaoded first. Downloading Gameupdates while playing is now possible, too. Thats cool if playing Singleplayer only. The downloaded Updates will be applied after exiting the game.
Source: http://store.steampowered.com/news/5856