Our Universal dates are Oct 4 - 8 (Thursday - Monday, flying back Monday evening) and I just learned that the CS will not be shown any night of HHN, so there's no way we can see it.
There's been rumors they'll use the system for some sort of show, or possibly continuously running type of thing for "100 years of horror" during HHN.
I thought the nighttime show was way better than a 5 fireworks and glorified movie ride, but I guess mileage may vary. (They seem to be slowly adding stuff to it over the summer)
We saw it in May, if it's the same as it was then, no you aren't really missing a must see attraction. I thought it was a cool lights/fireworks show. It's a really great way to end the evening, and certainly worth seeing if you can fit it in to your touring plans, also it's nice to be able to walk up 10-15 minutes before the start and get a great viewing spot () but it's not a once in lifetime amazing as some park closing Orlando fireworks shows..