I'm not a Mega Bus rider but does it typically make 25+ stops on a single journey? Along a route with a high number of stops, a few well placed intermediate stop to intermediate stop selections can seriously curtail through ridership to selected points.
That was one of the problems with passenger selected seat assignments last time and something they've noticed this time. You have to make sure you do this in a way that does not impact through ridership and revenue and doesn't require anyone to move at some point during the trip. Currently, the reservations system controls this function automatically. If it see a room being reserved for a portion of the trip, when it see another reservation for another portion of the trip, it will assign the same room to leave as much through space as possible. The same goes for coach seating. It calculates the space based upon maximums along the route between each pair. Without assigned seating, it calculates the "pure space." With assigned seating, you can only hope that intermediate trips come later or you can sell space to that intermediate pair...unless you only set aside certain seats for certain pairs. If that is the case, I don't really consider that "genuine seat selection." You are merely letting the passengers select from a pool of seats that has been offered to them.
That is why I'm betting all eyes are on 2103.