Ig, (may I call you Ig?)
You have one of the best ozone systems on your spa. It should quietly do it's job for the better part of a decade with no attention. I have relatives who..... never mind.
Anyway, it will do as the other posters have said: reduce the amount of chlorine you have to use, oxidize faster than chlorine alone, allow you to soak chlorine free (with occasional chlorine shocks and careful use of MPS).
It will reduce joint pain, inflammation, reduce fevers, and has been proven to reduce the chances of heart attack for those prone to it. WAIT - that's Aspirin. Sorry - I was good up till' this paragraph.
I need a nap.
:-/