I put the beta on my device and I've had an excellent experience. I've had some crashing and other strange occurrences but they are all minor. Frankly, I expected much worse. I took serious precautions, even backed up all of my icloud documents, notes, calendar, contacts, pictures, etc. because I've seen cases where a bad bug can corrupt icloud data.
But over all, it has significantly improved the battery life on my iPhone. I'm talking HUGE gains. And I am loving the ability to put minor Swift apps on my device as well.