I rarely have problems with Apple's OS updates, including the betas. There are always niggling little bugs, but they usually aren't show-stoppers for me. I think it depends on just a few factors:
Hardware: I don't upgrade often, but when I do I typically upgrade everything to the max. My 2013 iMac, which should be starting to feel long in the tooth, runs everything great... because I upgraded to a 3.5ghz Core i7, 32GB RAM, full SSD storage and the highest end (at the time) 4GB video card option.
If you scrape by on the minimums to save a few bucks (and I understand that everyone has a budget or a top line they're not willing to go over), you're going to suffer with performance issues down the road, and the computer will likely have a shorter life-span for you because of it.
Software: I've been to a few puppet shows in my time, so I've seen all the strings. I can't begin to guess how much software I've messed with in 30+ years of using Macs, and how many combinations of apps and utilities I've had running. The thing I learned long ago is that the more **** you shove in the bag, the greater the chance the bag bursts and you have a big stinking mess on your hands.
I run a somewhat lean system. I run Apple's stock apps whenever I possibly can. iTunes sucks, but I use it. There are better email, calendar, notes and reminders apps out there, but I use Apple's. Pages, Keynote, Numbers instead of MS Office. I run very few background and/or menubar apps, and I tend to quit apps when I'm done using them.
People who install every download they come across because it hacks the system to do something it probably shouldn't, does some minor outland task that takes a fraction of a second to do manually or simply because it "looks cool" are simply asking for problems. Nobody needs to have 2 different web browsers with 40+ tabs open in each running all the time.
People THINK they NEED XYZ app or utility, but the reality is that they generally don't. When their OS updates (beta or not) doesn't work, I find that many times what they mean is that their XYZ app/utility/hack no longer works, or works poorly. Cut back on the B.S. and the system generally runs better.
If you're fortunate enough to have multiple Macs, use one as your workbench and the other as a playground. I have a MBPro that I'm not afraid to install anything on or try anything outside my comfort zone. I can do that because it's not my main workhorse and it won't bother me to completely wipe it and re-install what I do need in a short amount of time.