I think LCDs can add a lot to pinball if done correctly but it's mostly in generating mood and much of this can wear off quickly especially for home use. More than 99% of pinball is found on the playfield and there is just no getting away from that core principle. For example, the LCD in TH was done very well but it's the gameplay that people ultimately judge the game on. People don't even mention the LCD when they praise TNA.
But now that LCDs are common, there is a downside that the industry is just coming to grips with: it places a tremendous burden on companies to do it correctly now. When done correctly it looks great but when thrown together by programmers at the last minute it can actually take away from the overall package. It eats up an increasingly larger part of the dev budget compared to what it adds to the total experience so in the end I'm not sure it it's a clear win for this artform overall.
All things considered, maybe Iron Maiden would have been better just having killer Eddie dots with same quality as MET?