I must agree that Wrath of Khan is a groundbreaking score for James Horner. I have seen the movie dozen times and I don't have any problem with Horner's approach. It works wonders. After all, the two different composers (established veteran vs novice) scored these first two Star Trek movies so the fact that they are different approaches is thus substantiated. Horner was going his own way, all new even for him at that time, and he gilded the sound track with youth, vigor and forcefulness.
So, for all these facts alone, 5 stars are just appropriate and although I am NOT James Horner's fan down-to-the-bone, this score asks for a huge hat-off.