I took Book A ride as part of my review of all the intercity carriers between Ottawa and Toronto and it was awful. It's the cheapest option but I will never take it again.
The biggest issue is that they have no decent stop locations. I stood in the location they described on the website (outside a particular store at STC) but the bus actually stopped further down the mall next to a pair of smelly dumpsters. Not a big deal for me since I saw the bus drive past and it stopped anyway, but one of the people getting on said that she had been waiting since the morning bus which she was unable to find before the departure time. Then in Peterborough, the driver announced we should be picking up 5 people, and although we sat on street outside a Tim Hortons for 15 minutes nobody showed up. Eventually when we departed some people came running across the parking lot, screaming that the bus was supposed to stop at the Tim's. This accounted for 3 people, so there were 2 others who never found the bus. The place where the bus stopped was not visible from the Tim's. Then at the Terry Fox terminal in Kanata (the only legitimate bus stop along the entire route), the guy in the row in front of me mentioned that the website tells you to wait at a particular platform, but the bus actually stops at a different platform completely on the opposite corner of the large bus terminal.
The driver was also an absolute maniac. The bus was limited to 109 km/h, which was the lowest of all the bus lines I tried, but I was on the Hwy 7 trip via Peterborough, so he was driving 109 km/h along the 80 km/h rural highway, viciously tailgating drivers to the point some of them pulled over to the side for fear of their lives. The bus also drove on shoulders which were not bus lanes to undertake traffic. And to top it off, the driver spent the whole time ranting about bad drivers.
My favourite carrier along the route is Red Arrow. I really appreciate the 2+1 seating arrangement with my wide shoulders, in my experience very friendly attendants and safe (but still efficient) drivers. They are the most expensive carrier but the tickets have fixed price of $81 including tax regardless of when you book so if you book close to the departure date (as I often do) it's only a few dollars more than the second tier carriers (Flixbus and Megabus).
Rider Express was also a nightmare with a maniac driver. Their buses are limited to 117 km/h which is unreasonably fast for a bus and encourages the drivers to drive like nutjobs on the 401. The bus itself was quite nice and although the stops were not marked, they are well described on the website and some are even in legitimate bus terminals like Toronto Union Terminal and Ottawa St Laurent Terminal.
My favourite carrier overall has been Keolis Orléans Express. They are nearly as good as Red Arrow (main difference being 2+2 seating so less shoulder space) but they're cheaper than Red Arrow which puts them top overall in my book.