This is just speculation on my part since there's no way to know what the 'truth' really is, but...in my experience and from my observations, NO feature that I know of has been a 'game changer'. What seems to have the greatest impact is sound quality and STYLES, STYLES, STYLES. I'm guessing that less than 10% of average home arranger players use the chord sequencer....or SAMPLING....or LOOPS...or any of the so-called super features. Why? In some cases they don't feel that the benefits are worth the hassle of learning to use/navigate the system and that it may even add to the performance workload. This may be different for 'pro's' but not many pro's use arranger keyboards (that statement may upset some people but it's the truth).

Bill (Abacus) is correct when he says that the volume manufacturers, ie. Yamaha and Korg, design these things for their primary (and target) market, the HOME PLAYER. As evidenced by even the responses HERE on THIS forum, most people are pretty satisfied with their offerings. Their design philosophy is driven by their marketing philosophy which is driven by the BUYING public. They are not going to be swayed very much by lone wolf techno-geeks whose ideas may be sound but buy one keyboard every 15 years. Regardless of what you think about the manufacturers, they DO know how to 'read the room'.

As far as "musicians having the final say in design decisions", I think most ARRANGER-playing musicians get more of a kick out of seeing/guessing/anticipating what the next iteration of their favorite 'board' will be. You know, like "surprise me". I mean Christmas wouldn't be nearly as exciting for a little kid if he already knew what was in the presents under the tree. JMO.

chas