I have the 16-35 f/2.8 II, it's not a waooow lens !
Having said that, it's a good one, very versatile, portrait at 35mm at f/2.8 are very good, bokeh is very nice and smooth, quite sharp in the middle at all aperture and and focal length, good for architecture, landscape, street photography, portrait, yes very versatile and a constant quality IQ, i use it only on FF camera.
Sure there is better lenses out there for a cheaper price, but over all, i'm use to use it so i know it's flaws and where it can give the best...
do i want to change it ? no ! even if i know it's not a wooww lens, but it's a good one which can still surprise me some time after so many years
just my 2 cents