I could draw an 2D technical drawing (for mechanical part) with LibreOffice Drawer once, althoug I had some difficullties in writing tolerances on measurement lines.. Succesfully.
I am pleased with it. I can do a lot of things like brochures, product inserts etc with it.
It's a quite useful uml-editor. Also it can be modified by an AddOn, so it can edit PDF's
Seems to me to be more of an attempt at a desktop publishing interface (like MS Publisher) than a strict graphics program. It has some good uses, in that respect (Scribus is best for that, though).
Not so good than MS Visio. Links still follow objects (if you move an object, lines still connected with other objects)