Chris Hannukainen of Pangaea CAD Solutions reminds me about their free DualCAD editor that reads and writes design files in MicroStation format.
It views, draws and edits elements, measures, and prints V7 and V8 DGN files in 2D. The included PDL lets you write macros.
(It used to also handle DWG files, hence the "dual cad" name, but Pangaea found the ODA libraries too cumbersome, and dropped DWG. As a result, the size of Dual CAD fell from 10MB to 2MB. With Dual CAD no longer dual-CAD, what to do about the name? Keep it, for it refers now to the dual uStn formats, V7 and V8. AutoCAD 2008/9 users can export their drawings to DGN, and then use DualCAD.)
It runs on Windows, but has been coded to work with the WINE Windows emulator on Linux. Download it free from here.
With DualCAD being a free MicroStation, who needs the $4000-MicroStation? Everybody else. Those who run vertical apps, need 3D, do programming, import AutoCAD drawings, and so on.
Think of Dual CAD as the AutoCAD LT of the MicroStation world. With one important difference: DualCAD is free.