I have been engineering/modeling/drafting for quite some time, and have had the opportunity to get acquanted with civil 3D.
The dynamic capability is what sets it apart. Dynamic means all profiles, cross sections and corriders tied to an alignment are updated AUTOMATICALLY if you change the alignment, FG profile or surface.
What a relief this is. Also, forget messing with text. If you want it to be 1/10", one setting and for what ever scale you want, the text will be right.
Civil 3D has become more akin to computer programming than drafting in many respects (styles, labels, properties and objects). It is such a drastic modification that it will take a tremendous effort in training and setup for many in the industry to become proficient.
I am lucky, in that I have no bottom line to contend with. But, the features and benifits are there to offset the investment.
One more note. Civil3D 2006 is very much like the Beta version. I would anticipate that 2008 is much better and more "mature".