The greatest improvement: no Touch Bar.
It helped me a lot while debugging and loved the customization it offered for the "static" keys on the right, but having no haptic feedback always caused me to miss the button unless I stared at it, killing the purpose greatly.
I also don't like how it's harder to operate than physical buttons. Too many times I hit the wrong spot on the bar and for example ended up putting my laptop to sleep instead of adjusting brightness. I've also tried to configure Ableton Live to do something useful with it (maybe mute/unmute tracks or control their volumes); but with little success.
Long story short: I'm happy to see it's gone.