I've flown IB
6253 (row 18) and 6250 (row 15) just a year ago....
The seats were preassigned as i'm iberia plus member. We (I and a friends also ibplus member) sat at the right side of the plane (2-4-2) and le leg room was quite decent (32" according to their website) but the central 4 seemed more "claustrophobic"
2 movies shown on main screens both in English and Spanish along with 6-8 audio channels. If you fly a -600 the screens will be TFT, if -300, CRT. The -600 fleet also haa a camera situated at the tail and it's shown live during take-off
My tip... you'll depart from JFK
at 21.15 and land in madrid arround 10.30 (but the flight time is only 7 hours) so bear that in mind for the jet lag
One meal service about 1 hour after take off and breakfast 1 hour before landing.... As said here, crew will misteriously disappear after meal service.... don't know what people expect, to make them sit next to you to chat?
The return leg takes off at 17.00 and meal is served arround 18.00 so depending on your meal habits you'll be hungry or not at all.... dinner will be served 1h.30/2h before landing. you'll be given the I94 form for inmigration about 1hour-30mins before landing
Enjoy Iberia, it's not that bad!