There are 2 versions available, a free version and a “pro” (Paid) Version. The free version is mainly for the use of building content for Google earth and is the same as the pro version. But the pro version comes with a few extras tools and you can load and save different formats, ie; 3ds, dwg, dfx, ect. The free version is good for learning the programs functions and to see if can fit into your work flow before purchasing the paid version.
It’s an easy program to learn and there are books and web sites with lots of tutorials, if you need it but you should be able to pick up the main functions in a afternoon. The important thing is to make sure your face normals are facing correctly if you are going to use the models to render in max.
Since there is a free version as with anything that’s free to the public there is good and bad stuff out there available on the google warehouse. If you use models from the warehouse you may have to do some work in skecthup before you import to max, mainly flipping faces and cleaning up geometry.
As with any program it all depends on the user what you get out of it. Sketchucation site is a great place to learn about this program. This link is a great look at what can be done with this program:
http://forums.sketchucation.com/viewtopic.php?f=81&t=33509
Hope this helps....