Learn Portuguese (Portugal): Que tal foi o concerto?

While como foi o concerto is also perfectly correct, que tal specifically asks for an opinion or an evaluation. It translates well to "What did you think of the concert?" and is a very natural way in Portugal to ask about an experience.

Why is the verb ser (foi) used here instead of estar (esteve)?

It is easy to forget that events like concerts, parties, or meetings always take the verb ser. Because a concert is an event that takes place rather than a physical object in a temporary state, we use foi to ask how it went.

Could I drop the verb and just say Que tal o concerto?

Yes! In everyday spoken Portuguese, it is very common to omit the verb entirely with this phrase. Asking Que tal o concerto? sounds very casual and natural.