I updated my Lumia 830 back when the build number was 10586.36, if I'm not mistaken. I'm a fairly new user of W10M, been using it for a bit more than a month. Currently rocking the .107 build, and I enrolled in the Fast Ring Insider.
I rarely experience app crashes, though it does happen once in a while, like how it was back in WP8.1. The crashes affects both WP8.1 apps as well as W10M apps.
The only advice I can give you is this: HARD RESET AFTER UPDATE, NO RESTORING FROM BACK UP.
This will solve 99% of the bugginess in W10M. Honestly speaking, I haven't found any bugs throughout my usage. Battery life is on par, if not better than it was in WP8.1.
Performance is generally much better than WP8.1, but in regards to apps, those apps that are meant for WP8.1 like the Windows Central app, 6tag, etc. will have some performance issue like taking longer to launch and resume from background, and it crashes more often than the apps built for W10M (though as I said earlier, crashes rarely occurs. But 80% of the crashes I experienced are from WP8.1 apps).
All in all, it's been a smooth sail for me. Just remember my advice, and you'll be alright.