I don't think it's as black and white as you might expect. I have seen anomalies that would be in line with being hacked, and that significantly improved after I moved to GOS. There are still a few anomalies that I am watching for at this time, and one thing that I can say is that after reading my logs I am absolutely not fully aware of the extent of GOS hardening and security. Those logs changed a bit since the last update and it points to security improvements.
Even those anomalies that I am looking out for have significantly reduced in frequencies even more over since the start of the year.
I see GOS as an extra layer of defence and I would likely still be experiencing more issues without a multi-layer approach and many decisions that I made in the last 6+ months have been about reducing my attack surface. It is both difficult to measure and has compounding effects over time. The downside is that I may be missing out on some great technologies that are more secure (e.g. sftp), but overall it's a net positive. Right now I'd rather miss-out for a while until I feel confident that what the technologies is doing have limited side-effects, or that they are avoided or mitigated.