I've personally moved to GIMP for my mapping needs. Primary reason is due to a 100% switch to Mac. Now that being said, previously I used Campaign Cartographer and a variety of the products from Profantasy. There are some on here that have had success with moving over to Mac and using a program like Parallels or Bootcamp in order to load a version of Windows that would allow them to continue using CC3 or some of the other products available for the Windows environment.

The 'fog of war' requirement may be best dealt with in other ways. I take it from your post that you intend to present your maps electronically. There are products available that will allow you to create a map and then apply the 'fog of war' concept within those packages. I've seen them demo'd at some of the gaming conventions so I know they are out there. Their product names escape me at this time but someone else may be able to help in that area.