There was a problem a few weeks ago where users on certain servers were reporting speed problems. The problem was tracked down to an internal router that wasn't performing up to specs, this was replaced and the problem was apparently resolved.
Personally, I have never had a speed issue with the sites I have hosted at DreamHost.
For more examples of sites hosted on DreamHost, you might want to check out some of the previous winners of the 'DreamHost Site of the Month' award at the URL below.
Save [color=#CC0000][b]$50[/b][/color] on DreamHost hosting using promo code [color=#CC0000][b]SAVEMONEY[/b][/color] ( Click for promo code details )