I'm an Alkan convert myself. Actually, I didn't need much converting - all it took was a listen to a midi rendering of the study "Allegro Barbaro" (op 35, no. 5) and I was hooked. I listened to several midi versions of his compositions before I heard any of his music actually recorded. I didn't even think the music was playable - pieces like Allegro Barbaro, Comme le Vent, and Le Chemin de Fer seemed to require superhuman feats of virtuosity. Then I bought Jack Gibbons' two disc recording of the complete op. 39 etudes. That set simply blew me away. The concerto and symphony for solo piano are both masterpieces of the literature and it's a shame they aren't programmed more often. Even after all the great recordings of Ronald Smith, Raymond Lewenthal, Jack Gibbons, and Marc-Andre Hamelin, Alkan is still confined to the ranks of piano esoterica, along with Medtner (too cerebral my ass, I love that stuff!), Sorabji (anti-musical? sure, that's why I love it!), Catoire (I want to hear more of this guy, right now!), and Busoni (too bad he didn't write more original music as opposed to transcriptions).
But of course, Alkan's music requires an unusual degree of commitment. It's uniquely difficult, I've heard it described as "the most difficult music prior to Godowsky. I wonder, it is un-pianistic? I can't play music of that level of difficulty, so I'm not in a position to know. We've heard reports from Liszt and Busoni that Alkan was a great pianist, so he, like Liszt, was probably brilliant at utilizing the strengths and weaknesses of the instrument. But a lot of his music, especially the studies, seem to push the performer beyond any reasonable expectations. I'm reminded of something Dmitri Feofanov wrote in the liner notes to his recording of the Klindworth arrangement of the first movement of the concerto for solo piano, when referring to the original version. "The whole movement was worked out with the iron hand of a composer giving no thought to considerations of pianistic convenience." Sounds rather damning, but when transcendent performers like Gibbons or Hamelin play it, that doesn't seem to matter. I'm guessing that Charles, genius-lunatic that he was, freely went beyond the limits of playability (at least beyond the limits of ordinary mortals) in search of artistic expression - a tendency common to the greatest and most innovative composers.