Not sure Bremen-Berlin will do well against the train which is three hours city centre to city centre. It often takes an hour just to get from Schoenefeld to the centre of Berlin.
Quite right, apaul, if the passenger's destination is central Berlin; however, Sch
önefeld is also a gateway to other parts of Brandenburg and Saxony, so if they're heading there, it's time saved.
Ryanair's choice of airports has caused much comment in the past; but some passengers' journeys are inevitably going to be easier without a slog into or out of a busy city centre.