I gave up trying to find a good 24-70mm L. I've owned five of them, and all were less than stellar. Many lens testers and experts have found the same issue, too many out of spec lenses.
If you have a good one, they are excellent as long as the curvature of field is not a issue for your usage. I'm not sure I'd waste my time/money on a new one, having seen the quality of the existing one five times. However, if there is a general positive agreement by the experts, I might bite.