Is it worth watching the ads?

I think so. Generally the rewards are quite good. I find the best rewards are via the helicopter and the x2 Campaign, which will double the earnings of your park for a couple of hours.

Every day you also can watch three videos in exchange for a spin of the ordinary vending machine - which normally costs 100 Tokens.

The game was developed purely that the developers cash in on selling ads (you watching them), more time is spent watching ads than playing the game. It should be called App Developer Tycoon. You get 1% of enjoyment and 99% watching previews of other developers games.