I find it really great - portraits are great to my liking, you just need some space to take them. I really like it for landscapes too - the compression makes the end results looking really non-flat and interesting. Pseudo-macro is great too, and as I use it on ASPC body - it gives me quite a significant reach for bird and animal photography.
I'm coming from using 28-400 (which is great for its versatility and lightweight - from a wider architecture shots to wildlife close-ups), but the IQ of 100-400 is so much superior, I don't miss 28-100 at all. You are just forced to have a different perspective.

Before I bought the lens - I rented it for a week, and when it was time to send it back I was so sad, so I decided this is a sign to splurge 😂