When I first started working remotely, it was a miracle. I finally remembered what it felt like to focus again. I hadn't been able to think so clearly and deeply since college. I had previously thought my mind was suffering early dementia, but it turns out it was just that standard office environment does that to me.
I will say I did miss some of the socialization. I had to consciously step up my outside-of-work socializing time. I think all but the most social people could do this if they made a conscious effort to maintain their social/mental health while working from home. Having young children at home also makes this difficult without a dedicated office and stay-at-home-watching-the-kids-full-time spouse. The big problem right now is people are not capable of compensating for the lack of in-work socializing with out-of-work socializing. I imagine that's extremely difficult for most people.
I think it allowing people to choose would give the biggest productivity boost. You do better in the office, but I was way less productive in the office. forcing people to do one or the other will hurt productivity.
But I live where land is cheap.
I've worked from home for 9 years and it took a long time to get to the point I felt just as proficient as I used to at the office. That didn't really happen until I had a dedicated office in my home, a good desk, a great monitor, and an amazing chair.