$500 via Verizon e-gift card (sent w/in 8 wks). Activation of 4G LTE/5G phone on One Unlimited for iPhone (all lines on account req'd on plan), 5G Do More, 5G Play More or 5G Get More plans req'd. Device must remain active for 45 days. $500 charge back if service cancelled w/in 12 mos or eligibility req's are no longer met. See vzw.com/bring-your-own-device for details. And for a limited time, we’ll waive your activation fee when you order through vzw.com or My Verizon app. You’ll see the one time charge waived as your “Due Today” amount at checkout.
Use Desktop Manager to backup your device, and also to install the upgrade. Try it for a week or so, and if you don't like it, then roll back to your previous configuration from the backup.
I was hesitant to upgrade from 5 to 6 on my Bold, since I had just activated it and was getting used to 5; but I have no regrets, and I'm not considering going back to 5. 6 is working well for me so far, and it's been well over a month (late June or early July when I installed 6).