Me, I am also someone who is always hesitating to "upgrade" to the newest IOS... I am always "1 version in retard" because I want always to work with a STABLE OS, be it IOS or macOS...
BUT: A friend of mine got a "new" iPhone SE changed by apple because of a charging-problem. helping him to install his backup on his "new" SE, we saw that this was only possible while installing IOS 12.
we both were very satisfied about IOS 12.01.
Even me upgraded some weeks later and I have to say, it works excellent on my SE 128GB.
It has gotten faster, running smoother and even battery time is now better than before.
I am very pleased and a happy User now. First time ever since 2005, that I faced the risk to use the "newest" OS.
upgraded also my "old" iPadPro 9,7 256GB and this works significant better than under IOS 11.6.1 as well.
Note also that apple claims that there were some important advances concerning security and privacy.
All in all, the best IOS I had ever on my IOS devices.
BUT: Neither my best friend nor me are power-users who install hundreds of apps and chase around in social networks, we just have installed round some dozens of apps.
regarding the comments about IOS 12 they are much better than that comments normally made about new IOS-Versions.
I join in to the comments already made here: You have to make a solid decision by yourself, depending on your personal needs. But me as someone as skeptical and hesitating as you about upgrading OS, I can only recommend to upgrade. For me, it is worth it and I am nearly sure that you will be glad with it.