I don't itemize, but I had my taxes done last week and the CPA's software is setup to do the comparison and my taxes will go down by $2,800 for the 2018 tax year. However, the IRS has adjusted the withholding tables too, so my paycheck is about $100 larger every two weeks, so it will only net me a $400 larger refund next year.
DD's estimate was much lower, only $300 less tax, and she does not itemize. But she plans to buy a house this summer, so she will have interest and property taxes as a write off next year. And even though we live in "Taxifornia", the interest and property tax write-off for her will likely only be about half of the next write-off cap.