I'm getting the same thing (Vancouver cable). Service is slowing down to 5-10mbit late afternoon and throughout the evenings. Streaming video from anywhere (YouTube, iTunes) is has become a frustrating experience on Teksavvy. Again.
I am experiencing significant slowdown in the evening. Typically after 8:00pm and lasting until 10:30 or 11:00. It is a real pain when trying to watch itunes tv shows or movies. Often get buffer times of 1 hour or more. I have noticed this quite regularly over the last week or two and always around the same times.