The problem is "how stable" is a personal opinion, different people have different standard. Also, beta can work well on one machine, but may be totally broken on the other. It's really hard to tell if this kind of early beta good for anyone's daily ops. For myself, I am OK. But I still won't recommend anyone to do so.
Unless you has very strong reason need HS now, even beta you still want it. e.g. For your GPU / eGPU. Otherwise, I will say better wait for few more months. The new APFS looks good, but also can be a trouble maker. Some hidden bug need time to dig out. Or even need time to build up. If you do worry about stability (that's why you ask), I think you better stay away from it for daily ops.
Or you may install it on an external drive, use it for few days, and then conclude if that's stable enough for you to daily use.