Generally cheaper than the train. Might or might not be faster depending on how many stops they have to make where you don't want to be. (they have to leave the freeway and travel to their stop which can eat a lot of time going places you don't care to be) Also depends on specific conditions of traffic, though in most cases the bus can detour around problems easier than the train.

Never really took Greyhound. I just drive now that I dont go alone. It was only reasonable as a one person trip for me.