Really

I don't have to imagine anything because I've used Maya (mainly for modeling and a bit for animation) and shortcut based actions for modeling (like Softimage and Houdini) beats marking menus by a long shot in terms of accessibility (which is something we ought to not ignore) - marking menus become tiresome after a while if one has to do modeling operations by the thousands per a session.
This as far as viewport interaction goes. Regarding the netview, being a newbie in this area I'd probably do best to just shut up about it, however I could see a problem with that also considering the huge number of nodes. Yes, I know that one can customize the marking menus, but I don't think (again from my newbie perspective) that there are a few most used nodes like it is the case with modeling operations so that one can just put those and for the rest use the Tab feature.
Also, one doesn't go berserk in the Netview like modelers often go in viewport, there you'll spend most of your time thinking and tweaking params not laying down nodes.
Anyway, bottom line is that like with many things, I don't have something against as long as it is extra/option and not a replacement, I'm just arguing why IMO is not an improvement over the current workflow.