I use Shaw, and just like Xpec, I lag most when someone is using bandwidth.
Namely torrent downloads eat away at the network, especially with 3 computers preforming 24/7 downloads.
Although Lunia is the only thing that I ever had problems with lagging, so I usually have to terminate the other systems downloads, and the lag is reduced tremendously. (Ex: I can actually connect to a square, but still dc, teleport ect.)
However any other game, or any network application works flawlessly, even if the other systems are draining the bandwidth.
I don't blame my ISP to be honest, and changing ISP's would be hard for me to do anyway, since it ties into Cable and Phone. (package)
Although my father thought of doing an upgrade to the second fastest package (dunno the speed, but I assume its T1)
I bet lunia would still lag like hell.