It helps. No vessel (without a similar system) is going to be ramming or harassing it, whereas it also has a very authoritive presence for anyone who happens to be in the area when one rocks up. Arguably it is more of a deterrence - though it could certainly be used for self-defence or as a warning device (i.e. a shot across the bow). 50cals could also achieve this, though they are less visible and impactful overall - especially towards larger vessels which may begin to appear more often in our EEZ.
If it is anything like the Typhoons, then they can be difficult to maintain, much like any system worth having.
I'm not an SME, I just happened to work on the ACPBs for a while in the past. After living in austere, I'm glad we are moving to the Arafura-class over the course of the decade.