Compared to various competitors, formZ's Hidden Line is quite bad. Often there are extra facets showing which I have to troubleshoot to find the best display resolution and/or faceting scheme (which may or may not work). Then if I have dimensions in the model, forget it, they look horrible in HL.
Lately I've been exporting my models as DWG and opening them in a--ahem--sketchy competitor. The hidden line here performs just like a shaded or wireframe mode. Zero lag when panning or moving the camera, rendered instantly. Dimensions are clean and I do not need to change any of the options (I almost always have to change options in the dimension styles . The same model/imported DWG in formZ takes about 10 seconds to generate the HL, which I could live with if I was able to seamlessly move around the model. But that's completely out of the question, the lag is unbearable.
I know HL was recently improved, and it is indeed better. But compared to the rest of the pack it's still no where near up to par.