Our taxes look remarkably similar to what I predicted over a year ago when the laws was first proposed. We no longer have enough deductions to itemize, so will have to take the new larger standard deduction. Tax rates went down but the brackets expanded to cover more income, so our gross total tax liability went up a little. Fortunately the increased child tax credit more than makes up for the difference (in this first year) so our net taxes went down a little. About $1400 down.
All of this is as predicted. If the rest of the law shakes out as expected, the scheduled changes to tax brackets over the next five years will take away most of that next year, all of it the year after that, and then start costing us more, relative to our liability under the old tax structure. Then some of our kids will start aging out of the child tax credit, which will cost us an additional $2,000 per kid (instead of the $1,000 it would have cost us under the old system).
Fortunately, I'm retired. FIRE folks who are spending down savings or Roth IRA contributions pay no income taxes, and folks spending down their taxable investment accounts only pay capital gains, which are generally better than income taxes.
The impending loss of our (newly enlarged) child tax credits does mean that our withdrawal order in retirement is suddenly a little different, which is a somewhat convoluted and non-obvious impact of the new tax law. We only have a few years of maximum kid credits coming our way before they age out at 17, so it makes sense for us to voluntarily incur additional income tax now, in order to utilize all of the offsetting child tax credit, while saving our tax-free options for after our kids age out and we no longer have the option to offset our tax liability.
Everyone's situation is different, of course, so don't take this advice as gospel. But in my family's situation, the TCJA lowered our 2018 taxes a bit because we earned boatloads of money. Next year, with lower income, we're expecting to pay far less in taxes than we paid this last year, but more than we would have paid without the new tax law going into effect.
So temporarily the TCJA was good to us, as expected.