The last Iberia flight I was on I was seated in first class - sullen flight attendents, really, really bad service, lousy food.
My wife had to fly in tourist class ;) and it was the worst experience flying she's ever had to endure. My experience was on Aerolineas Argentinas is a close second. I literally kissed the tarmac when I got off the plane - it was scarey.
The first couple of times I flew Iberia, I thought I was receiving awful service because I was a foreigner. Then a Spanish friend told me that they treat Spaniards even worse, and it is true that everybody in Spain hates the line. "Sullen" barely begins to describe their flight attendants...
I was in T4 a couple of weeks ago, having made the mistake of getting a ticket on Iberia for a short hop to BCN. The lines were incredibly long, the check-in machines were broken, and there was no staff - and they closed the flight 45 minutes ahead of departure, with the result that I missed the flight. They wouldn't give me my money back, even though it was their fault for not providing enough facilities (I was there in plenty of time). I think the flight must have gone empty, because I was one of a whole crowd that missed it. Another experience to remind me why I never fly Iberia, and why I should not be lured into attempting it again. You can find good last-minute fares, but that doesn't help if you can't even get on the flight.