Yes, many companies use 3D in marketing. It's huge value to see the product and be able to reduce cost ad produciton. Or putting data directly from engineering onto a catalog on a web site, rather than re-staging it all for the catalog.
There is also add-on value of using 3D, in that once a product is designed fully in 3D, that design can easily be re-used for the next customer with a similar requirement. Design re-use is a huge value.
Certainly the widest use is technically trained people like engineers. THis is not only because it landed on their desk first, but also because they have a mindset of exploring technology. Again, back to culture and mindset. I see many purchasing people receiving RFPs and dealing with 3D data just fine, even in small suppliers.
Absolutely not. Especially with the migration of products to lower price points and better ease of use, even small companies are using it. And as most anyone in a professional position these days can drive a computer and mouse, that person can also open a CAD file and rotate it to see some comment made by someone, and proabably add some of their own annotations. Maybe it's a marketing/packaging person or a sales person looking at a quote.
Some of the major appliance companies are evenusing now to help their repair people. Fairly complex machines. Especially at the higher pri-cepoint products - to justify the cost of implementation (assuming higher margin).
It's driven by design cycles first and foremost. So the most complex, multi-part, multi-assembly products are the leaders. THerefore it all started in automotive and aerospace. BUt it's now very big in any industry that has these kinds of products. MY survey results show industry adoption and it's expanding each year.
As you might imagine, I am not real keen about recommending a particular toolset without understanding your requirements. These are complex issues. BUt I would take a look at Materialize for STL among others.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.