The basic program is a free download, and the 'Pro' version is about $400 and change. The added functionality of the full version is a little esoteric in the context of how I use it. Among other things, it allows the user to import/export files with CAD and other 3D applications.
The basic SketchUp workspace
Learning the program is pretty intuitive. Anyone familiar with digital graphics applications will quickly be up and running simply by playing with the tools. I would encourage users to watch the tutorial videos, however, as they explain some of the less intuitive functions and reveal several alternate tools accessible only by mouse+keyboard commands.
The box stack below was easy enough to picture in my head, but sometimes I like to consult my eyeballs for a second opinion. This model took no more than five minutes to build during the estimate stage of a potential crating job.
Quick Foamcor box stack
Numerical commands are particularly useful, as these keyboard inputs will snap your shapes into exact dimensions. This feature works well for detailed or unusual build plans...
Cradle design for a fragile artwork needing even support
Cradle design in riding orientation
Actual crate packed with the cradle and artwork
...getting a head start on storage solutions before receiving the objects...
How much space will we need for this - exactly?
...and even preparing for the occasional shipping challenge. I made this simple model...
Virtual loaded truck
...to quickly formulate a loading plan that used every linear inch of a trailer. This was a close one, but we knew before the truck arrived that the load would fit, and the configuration of crates needed to make it happen.
Actual loaded truck
I've also used it to work on the design of a new warehouse facility at FAS. Once the warehouse model was built, it was just a matter of moving wall and door components around until we got what we wanted. The parallel projection 'camera' was useful for clean floorplans...
Another point of view
...the area calculator was useful for instant readings on the square footage of irregular spaces...
Area readings on display
...and even the less practical ability to zoom down into the space and look around from the inside became useful when I was working on presentations of a visible storage area.
A view inside our visible storage space - this hand-drawn look is one of
many rendering style options. The rendering is performed in real time, and
you can work with the model while such a custom style is assigned to it.
You really have to see one of these files open in the workspace to appreciate how cool it is to spin a model omnidirectionally and look at a situation from every angle.
There's an online repository in which a large community of SketchUp users share their models. I downloaded the ammonite model in this article's first image from an anonymous user in the Google 3D Warehouse.
3D Warehouse can be accessed from within the SketchUp workspace,
or from your internet browser
Amateur programmers have also been writing plugins that expand SketchUp's capabilities in the form of Ruby Scripts. One of them will generate cut lists from the components in your models. Others facilitate various types of animation, lighting effects and procedural modeling. You can customize the application with any number of these scripts, most of which are also free.
This kind of thing isn't everyone's cup of tea. But it's one more tool out there, and it wouldn't hurt a thing to take a look.