Sadly Greyhound is the only option for intercity travel (without a private vehicle) in many parts of Canada. In those places, it's generally OK if not overly comfortable. However, for long-haul travel (i.e. routes also served by air carriers), it's not advisable. Routes like Edmonton-Vancouver are rife with problems like people shooting heroin in the bathrooms, buses breaking down 200 km from anywhere and pax stranded on the side of the highway for hours, etc.
In general, Greyhound pax are people who can't afford to fly and can't afford a vehicle, which is 95% normal working-class people, but the 5% mentally unstable/criminals/drug addicts ruin it for everyone.