Can't say that I find this unlistenable, but I too was disappointed when it first came out, and have yet to really warm to this collection. Problem is, I think, that only two charts are by Gil, and it seems as if most of the album was made w/o him really having too much direct influence on the music. Still haven't heard the CD version though, so maybe that's a different animal.
Evans' next RCA album, There Comes A Time, was/is another matter entirely. To me, that's a great album, and an even greater CD. Whereas the Hendrix album seems mostly loud and unsubtle, monochromatic, even, TCAT is a multi-textured work of electronic/accoustic beauty, with a depth of detail that has continually rewarded years of close and repeated listening. It kinda sunk upon initial release (perhaps the much better hyped Hendrix side failed to meet anybody's expectations, and the followup was doomed to be ignored?), but it's by far the better album imo. I'd go so far as to call it a genuine masterpiece, especially in the expanded CD form. So much color....
Gil's conversion to/immersion in electronics was/still is a matter of no small contention, and has been vigorously discussed/debated over the years. If I were looking for ammo, I think I might pick the Hendrix album as an exhibit for the prosecution, and There Comes A Time as one for the defense.