I have been having performance issues with my DSL service for sometime (over a year). But, the problems are intermittant, so it has been difficult to pinpoint the cause or reproduce the problem consistently.
Here is some background
A summary of the problems ni July, 2008.
And an update in October, 2008. This was after weekend where the RTTs were horrible pretty much the entire weekend. (As usual, I was not generating or downloading traffic to any significant degree.)