Apple's beta software have been surprisingly very stable this year. I took the risk of updating all my daily devices to their respective 17 betas and aside from some performance hiccups every now and then, which also unfortunately would occur even in stable versions of last year's software, and battery drainage, which can be expected at this stage, they are running really well. I have only come across some small user facing bugs and that is amazing, considering these are only the very first betas. I am really impressed and believe things can only get better from now on. That being said, some of the issues are still present. Notification Center is still a mess. I really hope they will fix it until public release.