Sitting around for a bit over half an hour, I decided to go a bit further along the river to see if there were any better vantage points, and stumbled across a spectacular diffraction effect with light bouncing off one of the CBD's glass buildings a bit further downriver:
CBD light diffraction
After grabbing some snaps there, I headed to Wilson's Outlook to see what effects were to be had from there. While they weren't nearly as spectacular, the ND1000 filter made for an interesting landscape, including a blurred CityCat:
Morning fog from Wilson's Outlook
So the mantra of patience definitely paid off!