The change that I'm most interested in applying is the expansion of the "Saver's Credit" for low-to-mid-income taxpayers.  It increased the threshold for 50% by a bit (MFJ was $41,000, but now it is $48,000), plus the phase down is slower and more gradual (MFJ was totally phased out at $68,000, but now it is $83,000).

EDIT:  Oh crap, I just saw that doesn't start until 2027.  What is up with that?

SECOND EDIT:  Double crap.  I was reading an older version.  At first glance, the new law completely screwed up the Saver's Credit.