As someone who's been using Videotron for the better part of 6 years now, coverage isn't too much of an issue. Their network is pretty extensive from one end of Quebec to the ass end of Toronto. They're pretty solid in rural areas too, and if you do lose their main network, they have roaming agreements with the big 3. So, if you have 0 reception, chances are no one else does either.
As for their data speeds, they're pretty consistent and latency isn't horrendous surprisingly as I've been able to game online using my phone's hotspot feature. Though I wouldn't recommend twitchy games where that can make a difference.
And, I can't remember when was the last time I had to call in about a billing issue. My bill's been the same for the last 5 years.