I am quite disappointed in my 24-70, not because of optical performance or anything like that, but because it has amassed internal dust in the optics after not that much usage. Even worse is that it was a replacement for another copy (brand new from retailer) that had a rather large brownish piece of debris that looked like tobacco behind the front element. Must have been a bad batch of Monday products or something, but it is beyond me that the first one even passed inspections. None of my other RF lenses except for the RF 28 2.8 has any dust in them. The 28 2.8 I can understand and forgive as it is quite a complicated little budget lens. I can live with some dust in the optics, but what bothers me is the hit i take with resale value.
I think Nikon did a smart move with their new 24-70 which is internal focusing.