If it's not broke, don't fix it. Most multi rotor crashes are a result of prop failures. I thought that I was going to improve my craft by changing from APC to full carbon fiber props. Less than five minutes total into a second flight and the prop snapped off at the hub sending my craft to the ground. My craft was destroyed.
Upgrading to new firmware is risky, even more so if you do AP work. I love having Return to Home and Intelligent Orientation Control. I have Point of Interest set on my craft, but I have never tried it. I need more airspace so I don't muck things up...
I haven't had any major glitches from my firmware upgrades. Reading the horror stories doesn't give me confidence in my craft (especially after seeing how destructive this could be if it crashes into something or someone). My crashes, as mentioned was caused by a prop failure and not the flight system. I do wish that I had the firmware upgrade for loss of a prop when my flat hexa went down. I might have been able to save a lot of money.
It's a matter of choice. You'll have to reestablish trust in your craft, but by the time you do there will be another upgraded firmware. Personally, I like the new features. I'm just wary of my craft "dropping from the sky".