Look at the sheer # of connected users using the servers to download. It's a little unfair, it's like comparing some startup social networking site to MySpace/facebook...
This, imo, reflects poorly on Valve. Most of the time Steam is frustratingly slow. If he would expand Steams server capabilities I'd be as happy with Steam as I am with Impulse. Currently, I loathe Steam. Yes, Steam has a larger user base, but this is meaningless if it doesn't have the server base to keep up with its number of users.