It's one of those "historically significant" albums. I got it pretty recently, am still evaluating. On first listen I was unimpressed, but am now liking it better. The album starts out as kind of straight-ahead but transitions (Free Form Suite) to exploratory and eventually outside. I'm partial to Takayanagi's late weird/noisy material, and the final track (3d movement of Free Form Suite) is very much in that wheelhouse.
At this stage I'd say "interesting" rather than "essential", although that final track is really outstanding. At this point I overall prefer the Cool Jojo (straight-ahead, even Tristano style) and Takayanagi's Angry Waves 850113 (outside/noisy) albums somewhat. I don't regret getting this recording, however.