I agree
Barcelona is one of the few cities where I've had no compunctions about getting a taxi from the centre (typically around the Sants area) to the airport.
Little traffic early in the morning makes sure the trip is quick and cheap. (My own information is out of date now, but 6-7 years ago it was about 15 Euros)
Mind you, the BCN Airport Tryp does have some good offers on their website. Occasionally rooms are about 60Euros. That might sway me.