Thank you, that was excellent service.
'Ottimo' — 'OT-ti-mo'. Three syllables; double 't'; stress on first syllable.
Use when exiting the taxi after a pleasant or efficient journey, as a genuine compliment that encourages good service.
'È stato un ottimo servizio' uses 'essere' in the passato prossimo to describe a past experience. 'Ottimo' is the absolute superlative of 'buono' (good) — it means excellent/first-rate without needing 'molto'.
È stato un piacere viaggiare con lei.
It was a pleasure travelling with you.
Personal and warm; 'con lei' (with you, formal) is respectful.
La consiglio ai miei amici.
I'll recommend you to my friends.
The highest compliment for an Italian taxi driver.
Tornerò a usare il suo taxi.
I'll use your taxi again.
Signals repeat business — very appreciated.
Complimenting an Italian professional is genuinely appreciated and culturally important. Italian service workers take pride in their work — recognising good service creates a warm ending to the interaction and may get you the driver's card for future use.