To put it simply, yes, I think it's worth it. However, it depends on
what type of ship we're talking about. You can calculate the number of
ships RF will let you destroy this way: Say your RF rating against the
type of ship you're facing is 5. So you divide 100% by that number, and
get 20%. Now you deduct this from 100%, getting a final result of 80%.
This means there's an 80% chance of firing again (after destroying the
other ship). You should search the FAQ at the OG forum for detailed
stats on Rapidfire ratings for each ship type.