Interesting, but I sure as heck wish it could've been extended to 40mm if at all possible. Then you could easily get away with a 16-40 IS (and for sure if it had been the earlier 16-50 rumor) when you need IS more than anything and use it instead of 24-70 at times and the gap to a paired 70-300L or 70-200 wouldn't be too bad. 35mm to 70mm starts being a bit of a gap and sneaking it in for more portraits and such at 35mm is getting to be just a bit uncomfortable. EVen if it had a mediocre 35-40/50mm I wish they snuck that in. 45mm would've helped a ton.
The fact that it is f/4 and such a limited range does give hopes that it might perhaps deliver 24-70 II performance to the FF edges though. I do wish they had been able to tack on an extra 5-15mm focal length though, even if the performance there had been sub-par compared to the rest of the range, for people shots you can get away with it more and for nature stuff at least it's an emergency and likely better than quality from heavy crop. Although maybe it doesn't work that way and allowing to extend more would make the lower end suffer somehow (although I wouldn't think so, it could just keep extending and sliding and if the quality goes down more and more so be it, of course some would've screamed bloody murder about how the lens is junk because it's not so hot 40-45/50mm even though it's ultimate perfection 16-30mm).
Or if it wasn't going to go long, maybe 14-30mm f/4 IS would be more sense than 16-35mm f/4 IS since not sure 35mm is quite enough to quite make is dual purposed general lens. It's really kind of a pure wide angle on FF. And 14-30mm means you can dump Samyang 14mm and such. Hard to say though, 14mm is probably harder to pull off in a zoom especially without making it bulbous and weird and maybe 35mm gives JUST enough reach to at least make it a dual general wide landscape can just barely get away with it pairing with 70-200/300 at times. You can always pop in a light little 50mm 1.8 or 1.4 to cover the gap for the times non-stops lenss switching wouldn't be too much of a bother I guess, although in some cases that would be too slow and a bother.