Some things just work well the way they are and don't need change.

I think the biggest issue for me was that you couldn’t consistently find your current tab in one single place - you could scroll away your active tab amongst the rest of them, hiding the address bar.

Same. I really liked the new approach, but from the screenshots I figured all tabs would stack from the left making their position more predictable. Instead the entire tab field starts at the center and moves to the left for each new tab making all tabs moving targets.

I believe you can still select the old (well new/old design) design.

The new design is still the default in Beta 3; the change is just the addition of the "Separate Tab Bar" option.