This software is a must have for any serious game designer. It has most of the tools you could ask for. One of the things i like the most is the color system. You can use colors to represent things and working with colors can (massively) boost your productivity. Not just that you can choose colors for every object you create (including npcs, story or locations) but also that there's a color scheme on the program itself and it's not just black & white, which again helps boost your productivity (black & white are boring colors).
I'm actively using it to develop games. And i've found various other uses for the flow chart system, for example i've designed my programming code with it (i.e. in what order i will write which parts of the program and how they are connected). The program is also excellent for story-writing, actually beyond excellent. It's perfect for that.
With the templates system you can apply whatever properties you like to anything you create.
The entities system is used to create NPCs, Monsters, Items and other such objects which can be referenced or linked to locations and flow fragments (story parts)
With a little out-of-the-box thinking, this program can be super useful in more things than just game design. The flowchart system could help you design virtually anything you'd like.
If you're interested in the program i highly recommend you try out the 2 week trial, the learning curve is there, but it's not steep so you can definitely learn to use the program in under a week just by doing.
If what you're designing is really important to you, this program is definitely worth it's price.