it is amazing how aggressive and overlapping this board is getting. i was toying with plymouth yesterday too.
i think with the plymouth style GEOs, they are what I would consider to be 3rd tier GEOs, I have some but I am trying to be careful to focus in areas that I either live in or know something about otherwise it is hard to justify development, IMO
Roughly, I think of things like so:
Tier 1: New York, Chicago, Miami, etc
Tier 2: Cleveland, Tulsa, etc
Tier 3: Basically any city with 25,000 to 100,000 people in the US