Galaxy Fold 4
I never get tired of being able to use the front screen for simple browsing and quick access to things and then unfolding the phone to use the main screen for watching videos or playing games etc. I do have a few multi app pairs set up for certain specific scenarios (e.g. I have a Google calendar/Google keep app combo that is great for when I'm meal planning for the week and want to be able to add items to a grocery list at the same time). I truly don't think I would be happy going back to a non-folding phone in the future.
I dislike the battery life of the phone. That's probably my biggest complaint and honestly it's not unmanageable. I've always got a giant 21,000 mAh battery pack in my backpack anyway so charging the phone a bit during the day if I've been hammering the battery watching YouTube for example isn't a problem for me. I'm a ideal world the battery life would be better and this wouldn't be necessary but it's not the end of the world.
The under-display camera on the inner screen is truly terrible also but I almost exclusively use it for video chatting which already is bad quality usually just due to connectivity so it really doesn't bother me. If I were to take selfies (which I just don't do) I would use the camera on the front display. It is possible to unfold the screen and use the main cameras for selfies but as I said, I'm not a selfie taking kind of person.