You can load the Lidar using the ERDAS img format, I believe. This is done in Data Acquisition in Ss2 and under the Terrain tools in Ss3/4. There were issues in certain versions of Ss2 with units and vertical datums which may or may not have been resolved. Files would come in using metric elevations with US Feet northing and eastings. A transformation of the surface was required to correct this after import.
However, while these files can be found on the USGS Seamless Map server, the coverages provided in these files appears to have gotten larger since I first started using this method. The result being that the software frequently crashes when trying to save to a Native DTM.
We happen to have a single seat of Descartes, which is where Bentley has decided to implement the ability to perform dynamic, level of detail resolution of terrain models. These level of detail modes thin the points as you zoom out and restore additional points as you zoom in. Within this toolset is a mode to save a subset of an img coverage to a new terrain model, with an option to preserve all points or using thinned points. As an aside, Descartes also has tools for vectorizing ground lidar (laser scanned) to 3D elements. Any company that may decide to use scanned data might find a seat of Descartes worth purchasing.
The ERDAS files are available in various resolutions but not all resolutions are available in all locations. I believe the usual resolution was 1/3 second of arc (as provided in traditional DEM files) with is somewhere around a 10 meter grid (+/-30') and the tightest spacing sometimes available is 1/9 seconds of arc - 3 meter/10' grid. When used, the triangles often create zig-zag contours is used for small scale modeling. I have found them to be pretty accurate and when combined with actual survey data, the edges can be made to blend without too much efforts.