Hi Ullearn,
First, MapSource is a program that handles maps for a Garmin receiver, not the maps themselves. When you buy a map set (probably City Navigator), the program comes with it.
Basic receivers like the Etrex H do not handle maps. They can navigate point-to-point, following straight lines between the waypoints that you download from ACA. The Waypoint Manager and several free programs can load these waypoints into the receiver.
Mapping receivers like the other Etrexes use MapSource to load the maps. You see exactly where you are on the map as you ride along. All but the least expensive have enough memory to hold maps to cross the country and do automatic routing, following the roads with turn-by-turn guidance.
The GPS Data User Guide gives a lot more detail about all this.
There are third-party maps, mostly outside the US where Garmin's coverage is spotty. There are also some open-source individual maps and programs, which I do not recommend for the novice unless you are a computer geek. If you are one, you will easily find these.
Cell-phone GPS is coming on strong, but does not yet offer the complete self-contained function on your handlebar that the dedicated receiver provide, especially in remote areas.
I am not sure just what about the Garmin business model you dislike. It has certainly been successful. They have not fooled all of their customers all of the time and they have plenty of competition to keep them on their toes.
Do browse this forum for much more about using GPSRs on long bike rides.
Fred