And it's next to impossible to move to the rent controlled side of Berlin. The reality of rent control is it's a handout for the people who already live there at the expense of those that wish to move there.

I don't see how that is particularly legitimate argument against rent control as that is how the housing market works in general. The difference is that if you buy an apartment you also get appreciation.

New development is occurring in Berlin because the rent control does not apply to new units and it's on purpose. (Although didn't the rent control policy get voided by some court?).

As I understand it, and I'm not sure I do, the "you can't increase rent by that much" law got knocked down, and the govt response was to buy a bunch of properties and offer them for rent at rent-controlled prices.

Interesting times. It'll be fascinating to see this play out. Like a social experiment on rent control.