I haven't explored much of the new world of 3D PDFs in Acrobat as yet. I just came across these files available via the article on Bentley's site: BE Awards Nominee Rebuilds I-35W Bridge.
The article covers the use of a range of technologies to help designers and engineers detail these complex bridge structures. With the growing demand for these structures in replacing aging infrastructure, bringing processes like this improves the speed and accuracy of the design, detailing and analysis.
Here are a few quick screen grabs of the two 3D PDFs on the site:
The ease of navigating around the 3D PDFs as objects is great and the possibilities for utilising the portability of these files is something we should all look at more closely. There are a few different modes to view the models, not as many as Sketchup say, but they do impart a different character which can help.