Taxi's multiball is so well designed, because it's the only multiball that I can think of where you get 2 balls on the playfield & haven't "technically" started mutiball yet.
That requires you to re-lock both balls in the saucers within a short amount of time (music increasing in intensity as you fail away), get your little lightshow & song-and-dance for accomplishing that, then both balls are ejected for you to HAMMER the ramps for 300K point jackpots. Hard work for big rewards. That's a well coded game.
Easy & constant mutiballs are the absolute worst thing about modern coding on some titles. If it's too easy it's to achieve, it's not appealing at all to me.