Very little detail yet that I've seen. Cynically, I expect part of the "it's going to take two years to figure it out" is actually a bit of realpolitik in action. If they suddenly said, "We're going to base it on household income from 6th April", then all of those couples on £49k each would instantly lose the benefit. This way, the Tories might gain a small bit of extra support from the individuals who will no longer lose their child benefit for earning £60k, and they don't lose support from the households whose joint income would see them go above the threshold.
Good spot. I think payroll might have screwed up. All I did to get that figure was check a couple of payslips from the end of last year with January and February. My net pay increased by ~£112.50, so I doubled it to include my wife, who's on a similar salary.
Crunching the numbers, it looks like payroll reduced my NI by the correct amount, but they have also reduced my tax by that amount again. So unless there's something else at play that accounts for the reduction in tax as well as NI, I'm now underpaying tax…
So it's not £600 per month better off as a household, more like ~£330 (this is with the two NI reductions and the full child benefit allowance).
Still, as others have said in this thread and the other one, it just about accounts for the increase in CoL.