After five days with the add-on, my thoughts.
Good: routed me off the DVP (and back on again) to successfully avoid a slow-down; it updated a route “en-route” due to new traffic information.
Bad: doesn’t show that the Danforth is closed this weekend for Taste of the Danforth (the image below shows today’s data, Bloor Street / Danforth Avenue closure absent).
In closing: good for knowing about Toronto highway traffic, poor for knowing about city road closures.
The traffic data is provided by Inrix, so the quality of this data is the limiting factor. Inrix, which has its own traffic application for the iPhone, lists the following coverage areas in Ontario: Burlington, Mississauga, Niagara, Ottawa & Toronto.