It is no longer years ago, it is now.
America West two years ago tried rational fares as a pseudo-major. It worked, and they're on the way to success.
Alaska ditto last year and ditto.
Delta shows a great deal of sense in realizing that you can raise total income by evening out your fares, so that last minute travelers are not screwed. Very few top fares are sold by Delta; if they can increase the medium fare sales enough they will make more money with a rational fare structure, especially if those seats replace super-cheapies.
Since I always know far in advance my travel dates, and always stay over Saturdays, the current system worked for me. But rational fares are likely to make airlines more money in the long run, and be more competitive with the newer airlines who have always been rationally fared.
** It's not the RASM. It's not the CASM. It's the DIFFERENCE between the RASM and the CASM. ** DUH!