i wasn't the one hoping for a 24-70/4, but the new 28-70/2.8 is a pass for me. Never say never, but I won't pre-order it. Small, light, good IQ and f/2.8 are all plusses, but the main use case for the lens for me would have to be travel, and I would definitely miss the few mm on the wide and even more the long end. I use the 24-105/4L as my standard zoom for travel, and for that use case ~25% of my shots with it are wider than 28mm, and ~45% of my shots are longer than 70mm. I don't typically need f/2.8 for travel, if I need faster than f/4, one stop isn't enough so I bring the 24/1.8 along.
Vignette is readily correctable and little cost unless you're already at really high ISO. I don't get why people have an issue with forced correction of distortion – all rectilinear wide lenses have it, and there's no inherent advantage to correcting it with glass instead of silicon. I tested the RF 14-35/4 against the EF 11-24/4, the former after correction was just as sharp in the corners as the latter at 14mm, and the 11-24 doesn't really have distortion to correct at that focal length.
Plus, I already have three standard RF zooms (24-105/4, 24-105/2.8, 28-70/2), so I really don't need a fourth. The only real use case I can see for me would be on the R8 as a second body when I'm shooting with the R3 and 100-300/2.8. So far, though, swapping on the 24-105/2.8 has bee working fine.
More generally regarding the lens, it's got weather sealing (second non-L lens to get it), and Canon says it has L-series optical quality. Things like that are good news for everyone!