If you're using PathFinder in OSX you might see problems when using Mission Control and the PathFinder Desktop replacement.
With the last version, Mission control would not show the spaces-control elements, so you were not able to add or remove a space.
With the current version, this seems to work, but if you changed the Desktop background image, this is broken.
The Pathfinder Development team needs to improve here...
Again: this only happens, if you use the PathfinderDesktop!