First of all, let me tell you that I would update my phone. To me 0 day fix is a must. But, that just me. On the other hand this exploit was used against human rights activist (I guess, you know the story) and generally it may depend on the profile of the potential victim and one's knowledge to make this decision.

• You are right: The vast majority. Nevertheless, it is always advised to make a backup of important data. I am not against update, I just wrote "Don't update on the run, if you highly rely on your device". It may wait a couple of hours or even days as it is unlikely that your device is infected.
  Also, you cannot be sure from which version a user will make the update and how it affects the current state of his/her device. If you have an access to the computer and can fix eventual problems on your own, go for it. However, there is no reason to panic.
• In terms of jailbreaking iPhones, let me keep it this way: it is your phone, it is legal and you may want to use it without any restrictions. I would not limit it to 'teenagers'. People still do it. Personally, I don't, because (despite all problems) I use Android ;)
  BTW now I can see your post with a link about this topic. I missed it before, unfortunately.