I had the older version of Cosmographer, and upgraded to the version 3. First off, I have to say I've not been a big fan of it. When I originally purchased it, I was hoping for a mapping tool that would be relatively friendly for non-architectually inclined people. I wanted to abilty to be able to draw a shape, and then place the images on my deckplan that suited what I was looking for.
With that being said, I have to admit that the newer version is no improvement over the older one. There are some very nice and colorful templates, but the amount of effore required to use the tool to draw simple deckplans far outweighs the pretty pictures. I can do more, with just Visio, than I can with Cosmographer.
For those that remember, D&D put out a tool called Core Rules. Part of the application was a mapping program. It produced quite readable maps and drawings that just about anyone could do. It wasn't a super-high quality application like Cosmographer, but in most every way it is superior - it allows you to jump in and to be creative with the game while not having to spend a large amount of time just trying to master your drawing tool.
So from this gaming enthusiast, I have to give it a big 2-Thumbs down. It's kinda pretty, but mostly useless to the average or casual gamer who wants to create useful documents for their game.