I didn't even get far enough into it to be annoyed by any of the content - it's just the technical side of things that just doesn't seem to work for me. Here's my setup:
I have a Facebook account. With that account, I'm managing several pages. One of these pages is one I'm just experimenting with before doing anything serious on one of the other pages. I'm just posting random photos to the experimental page every once in a while, so this one could benefit from integration with Instagram.
1. I installed the Instagram app, logged in with Facebook, and instantly ended up with an account set up with my Facebook data - profile image, name, contact data. Within a few hours, I already had following requests by people I know, although I had set my profile to "private" by then. Looks as if at least some identifying information such as mail address or the fact that I'm using a certain Facebook account to sign is is considered to be exempt from privacy.
2. To set up a separate Instagram profile for my photography, I really had to search through the app. Eventually, I found out that first navigating to the profile tab and then tapping the username brings up an account picker with "Add Account" as one of its options. Tapping that, I was able to sign in with Facebook again and then choose one of the pages I'm managing. Again, most of the information was filled automatically, and I ended up with a second Instagram account. I could also switch freely between the two.
3. Apparently, what was not automatically filled in when creating this second account was the integration with Facebook itself. Instagram's own help page states that, to crosspost to a Facebook page, you have to open "Settings", then tap "Account", then "Linked Accounts", then "Facebook", then choose the correct page among all the options. Overly complicated (also because I had to sign in with Facebook several times in the process), but eventually everything seemed to be set up.
4. Then I created my first Instagram post - and it ended up being displayed in my personal Facebook profile feed instead of the page's feed. I double-checked my settings in the app, and it definitely was set to share to the page - but as often as I tried, it didn't. While sharing, it would even display my full name next to the sharing toggle, with no way to change it at that point.
5. I googled for help, and found a page describing some potential solutions - including the obvious idea of signing out and in again, "Unlinking" (which brought up a weirdly worded warning message), but also the idea of tapping "Edit profile" in the Instagram app, then setting the proper Facebook page there. No idea why that is even necessary after all the hoops I jumped through before, but I did that as well.
Eventually, I got integration to work. Instagram posts now end up in the correct Facebook feed. However, I seem to have lost access to my personal Instagram profile in the process. Adding an account in the app no longer offers "Sign in with Facebook" - and even trying to sign in via an incognito browser window on my PC just leads straight to the second profile I created. No matter what I try now, my personal Instagram profile is completely inaccessible to me. What gives?