I have Fractal Mapper and use it a fair amount (The mapper I use most often is Dungeon Crafter - it does a better job for interiors.) I did the campaign map for my homebrew world using it, the multiple choices for fractal shapes was very useful in that regard. Islands and continents are easy, and I like the way the landforms come out.
Fractal World Explorer I would use for games like Star Wars, Traveller, or Dragonstar, where a quick and dirty world map and spherical projection of same is more useful than a highly detailed map. I don't especially like the way it designs worlds (The continents just look wrong), but the maps are pretty. I wish there was a way to use the two programs in tandem.
Over all I like it, and do most of my wilderness mapping on it.
The Auld Grump