I have flown back and forth to Madrid loads of times in the past 2.5 years and I never looked forward to Iberia in Y irrespective of direction flown. The reasons for this are as follows:

-- Cabin crew do not seem that friendly, just going through the motions
-- If you want any food, you need to buy it (the main reason I stuff my face in the lounge before boarding)
-- No complimentary drinks offered. I once asked for water and it took 20-30 mins for them to get that.
-- Cannot use portable electronics at all times while seated, even in flight mode, like you can on BA
-- Flying IB from MAD to LHR doesn't give fast track security whereas using BA does
-- Legroom on IB flights seems to be very tight (I'm not tall), to the point where I started grabbing emergency exit row seat over and over
-- Flying IB to LHR means using T4 and not T4S, and T4's lounge is not a patch on the international terminal one
-- IB play that old and dreadful music during approach and landing
-- Apart from flying one of their then-new A330s last summer once or twice, the planes they use and interior seems old and in need of a refurb