Like you it was my first IB long-haul experience recently, to and from Havana in Business. Paid with Avios during their spring sale. The hard product is excellent, with plenty of personal space, flat beds and direct aisle access for everyone. The IFE system is user friendly and loaded with plenty of movies. Good headphones, too. However, I would have expected more in the service department. Crew members varied between robotic to disinterested both ways, after the meal service ended you needed to hunt down a top-up or even water. The pre-landing 'light meal' was thin, as was the breakfast on the return leg before touchdown. I've had better on short haul flights in Economy. On the upside the quality of the main meal was excellent both directions, as was the selection of wines. Just wish they were a bit more proactive in enquiring whether you're in need of anything - most people would just ask for a bottle of water.
IB appears to have a great punctuality record, Barajas is a seriously impressive home airport with oodles of space and good flying weather. Aircraft interiors are good, lounges are good. Crews need motivation and then it would be amongst the top 3 European airlines?