- It ensures a "realistic" layout for your map, at least to start. Then you can modify the heck out of things like woods, swamps, and lakes as you see fit. generally I try to minimize the number of "It's Magic!" type features on a large-scale map - no deserts next to jungles next to arctic regions. I don't mind them on a small scale, but on a larger level I steer away from them.
- I think it adds another layer of discovery for the players if they can figure out where they "really" are.
- It lets you get familiar with a part of the world you may not know well on a local level. This is just a side benefit with no direct impact on the campaign but it makes it a little more interesting for me.
Right now I have three thoughts on where to set the new campaign.
- Japan - this is what is referenced in Jeff's blog and I kind of like the idea of a conventional D&D game using a map of Japan. There is enough interesting terrain there, plus if the PC's get into a traveling mood then we have the Asian landmass to explore including some interesting peninsulas and a good-sized desert - who says you can't have pyramids in Mongolia? That big bay/gulf just west of the Korean peninsula looks interesting too.
- Australia - The east or west coast could serve as a Euorpe/Hyboria/Flanaess analog with the interesting twist of your viking-style barbarians coming from the south - "Oh no the Southmen are coming". Plus there are several large islands and the various island chains nearby which could be turned into the fortresses of evil wizards or the lairs of dragons- maybe the Solomons become the Dragon Isles.
- Seattle/Vancouver Region - this is a little smaller scale than the other two but it is an interesting area geographically, plus it includes a volcano - always a plus. I am moderately familiar with the region from various Shadowrun campaigns but oddly enough a D&D game tends to cover a wider area than a typical Shadowrun game where characters may never leave the city. I have some other campaign ideas that might make this option the most interesting down the road.