Greyhound is decent if you want to get to somewhere pretty close- I think going from Toronto to Ottawa would be a good distance! That would be around 5 hours. If, however, you want to go farther than that I think taking the VIARail would be more comfortable.
I went to Montreal via Greyhound and it was a pretty decent trip- the busses were all on time, the greyhound was clean and spacious enough, plus there was good AC the entire time. The wifi is dead to me. I do like the scenery as we passed by cities like Tweed and such.
We had to transfer at Ottawa, and the total duration for the trip was around 7 - 9 hours, depending on traffic. I get intense motion sickness, so around the last hour I felt like I was going to die. We had a rest stop every 2 or 3 hours in a seedy-looking restaurant in the middle of nowhere, but the washroom was sufficiently sized for all 10012414 passengers in the Greyhound.
P.S. you probably shouldn't eat before going on the Greyhound. It's better if your stomach is begging for food rather than begging for a toilet- don't use the toilet in the Greyhound unless you want the stench of your defecate to permeate the entire bus and you want EVERYONE to know who did it.