IB is generally considered to be one of the worst airlines in Y for trans-Atlantic travel; people pick it because it is much cheaper than the alternatives, not because of the amenities. Expect the worst, and IB will most likely exceed your expectations (unfortunately this means it will be worse than you imagined it could be). I've never flown IB in Y, but have flown it once in J (and never again). Their F service was quite good, but that is long gone. The real problem with IB is if you have any need for ground handling in Spain, then it becomes truly hellish (inflight service is great by comparison, though still below almost every other airline).