Arenal.net is an agent, I'm pretty sure they don't actually run the shuttles. From what I could tell, they are large and well known, and probably as good as any. My wife and daughter used Interbus, I don't remember who we booked it through, but they had no problems. You will have to take a cab to the restaurant nearby that they use as their 'station'. And the cabbie won't be thrilled about a 1/2 mile fare either, but so it goes. The last time we went, customs took about 2 minutes. With customs, immigration, and baggage claim, we were out of the airport within 15-20 minutes of getting off the plane. As previously stated, that probably varies depending on how many flights arrive at the same time.