I was with Bell prior to switching to Teksavvy DSL in December 2007. The only reason I switched was because of the impending 60GB cap. I never had any serious technical issues with Bell but there was no way I was going to live with a bandwidth cap.
During my time with Teksavvy DSL, they have shown themselves to be a very capable company when dealing with issues while growing at a fast rate. I've had more downtime with TSI than I ever did with Bell but I'm willing to put up with the occasional outage because Rocky et al are fighting to make sure I can use the internet the way I want to while paying a fair price.