urbanis, for regional buses, i tried bagging (with seatpost removed and carried in my backpack to make it lighter). overall, my bike is just too heavy to carry for more than extremely short distances. and the bag handle is an awful way to carry it, as it forces the weight onto a few fingers, where as holding from the main bar distributes weight better. the only other use i thought i would get out of the bag was preventing scratching between the frame and luggage compartment, but i don't think it does much there, the bike probably doesn't move.
the worst part about bagging was i was reluctant to take it out of the bag (to avoid having to bag again) when making a connection from a bus to a train, and i had an awful time carrying it.
i already don't need the bag for amtrak. i'm not trying to hide that its a bike from bus companies. the bag is a bit bulky rolled up. so i'm not going to use the bag at all from now on. and fold it at the last minute when boarding bus. unfold it and roll the bike with the seatpost removed for making connections. the best strategy is to make it very quick to fold and unfold, without any bags or straps to have to mess with.
the only remaining feature of the bag is covering the chain and oily parts of bike, if you wanted to put other luggage on top of it, say in the trunk of your car.