On macOS there were some issues but I can't say exactly because I returned my AirPods Pro 3.
Other than the missing artwork and label, with AirPods Pro 3 on iOS 18 you also can't see the battery level, you can't take a Hearing Test, and more. After iOS 18.7.1 was released and didn't address any of these issues I reached out to Apple who said they wouldn't be adding any further support to iOS 18. So I returned my AirPods Pro 3, an easy decision. Just not worth the hassle for me.
What about iOS 26 kept you away? I was hesitant when I got APP3, but was pleasantly surprised by how many longstanding issues with responsiveness and functionality it fixed for me (iPhone 15 Pro Max user).
I assume it's because of Liquid Glass. It's absolutely undercooked as a design system, but Apple knows which way its bread is buttered. So Liquid Glass on iOS is where it's the least bad, and I switched there knowing that. It was exactly as I thought: a regression in most places, but still manageable because Apple is laser-focused on the iPhone.
I didn't upgrade my Mac and at this point I'm wondering if I'll ever be tempted to update until I see what they do with macOS 27.
I guess you could ask "what about iOS 26 would make me want to upgrade?" My answer: nothing. Definitely not to get a slower and bugger UI, nor to get full support for headphones I could simply return for a full refund. I'm using iPhone 16 Pro.