Ha, I also give it a 6, but my 6 meant "lots of weak parts but ultimately narrowly succeeds."
If they had been able to make one of those pirates read as a specific, unique character and not just "generic buffoon type", it really could have worked.
Or if they'd just skipped over that whole middle sequence. We didn't need it. We could have had that holding cell scene -- "Alpha Braga IV?" "Alpha Braga IV!" -- and then the next time we see them they're in command of the ship (knowing look: "Alpha Braga IV"). The interesting story was Spock, Chapel, T'Pring, and Angel, we could have used more time there, and we can just jump over the mechanics in the other plot.