Took the 6:30 Megabus from Toronto to Montreal on a Saturday morning. The ride from Toronto to Kingston was smooth and generally an okay ride once we got started. Once we left Kingston and switched drives, we began going far slower, and arrived in Montreal later than our expected arrival time, even though there was no traffic on the road or poor weather conditions at all.
The tables on the buses are tiny, so don't expect to be able to set up a laptop or get too much work done on it - even the seats with tables that require a $5/person reservation fee. Most people choose to sit upstairs; there is a washroom downstairs, but also fewer seats.
The wifi was not reliable, so don't go on with a full expectation of surfing the internet the entire time. For the price of around $120 for 3 tickets booked a week or two before, I'd say it was an okay deal.