I am about half way through getting my first Civil 3D project ready for first submittal. It is a VERY steep learning curve, but I am liking the program more as I keep using it. It is producing excellent surfaces compared to what we are used to getting from LDDT 2k5. It has proven difficult to get the street profiles to appear labeled the way I prefer, but once done, the settings are saved and can be reused in future drawings do much of the time spent is a one-time thing. The Civil 3D board at AUGI is getting busy at last as more people are starting to use the program for the first time and find questions.
I think that with the next release, LDDT will be available as stand alone or be packaged with Civil 3D instead of Civil Design. Civil design will be still be available as part of a package, probably to make up for the lack of Hydrology or Pipe Works in Civil 3D. If / when 3D gets these modules, Civil Design will go away, so I would suggest start getting used to Civil 3D now.