My partner and I have flown Iberia (or subsidiaries) ten times, all economy. The first was Washington Dulles to Madrid before 2013 because we could connect to Budapest with Malev (went belly up 2013) so it was long-haul Iberia proper, excellent service but mostly empty seats and that's what got Iberia into trouble until BA bought them and diverted most long-haul flights via Heathrow. The irony for us is we flew Iberia specifically to avoid Heathrow. Finnair is developing a similar pattern with BA.
In October 2015 we flew Iberia Express Madrid to Barcelona and everything was good, flight on time, used Iberia lounge in Madrid. October last year and again October 2017 we flew Iberia Budapest tp Madrid, 3 hours in their lounge which is good but limited food and drink options, then subsidiary Air Nostrum Madrid to Malaga, then one week later the exact reverse.
Iberia short haul (Budapest to Madrid is 3 hours) uses Airbus A319, 320 or 321 just like every other carrier with NO entertainment and they even make you pay for water. Not likely to go under financially but on the last flight I noticed no one bought anything.
Air Nostrum uses the CRJ 1000 which seats 100 in 25 rows of four A, C, D and F. They don't seem to be as concerned with on-time departure as big Iberia but the flight from Malaga to Madrid was scheduled 75 minutes and took 45 so who cares? If you are looking at close connections from Air Nostrum to another airline in Madrid including Iberia I would allow at least 90 minutes to get your baggage across, 2 hours if its not all within T4.
One thing we've noticed about all these flight is the staff seems very cheerful. Also if you can't snack before the flight and do buy food on-board its OK just expensive.