I miss having clear separation between the time/space for work and time/space for leisure. I do keep the same hours but even my commute (provided that it isn't horrible) has the value of telling my brain "work starts now" in the morning and then "work ends now" at the end of the day.
There's not much I miss about the office per-se. Maybe a few small things, like having a Keurig style coffee machine at work, where at home I still use an old fashioned drip coffee maker, and setting that up and brewing a whole pot is more effort, when I just want my first morning cup of joe. First world problems though, right?
More meaningful, is that I don't necessarily like being stuck in my apartment all the time. I like being home, but I need to get out... so in the past, when working from home a lot, I would frequently go sit at Starbucks or the cafe at Barnes & Noble, etc., and work there some portion of the day, just to get out, be around other people, etc. Now, that's not even an option.
I do try to make up for it by doing more bike riding and running, which is an opportunity to get out. But the weather doesn't always cooperate. Take today, where it's gray, raining, and kinda chilly here in Chapel Hill. I probably won't go running or riding today.
Otherwise, it's nice to get back the hour and a half or so I'd otherwise spending commuting to the office each day, and not having to spend as much money on gas. I can also dress more casually when working at home.
As others said, clear separation of home|work. Also, food is too close and remote desktop lags. But overall, working from home is much better than working in a cubicle with 500 people.
I miss casual interactions while getting coffee.
Also exercise. All the gyms are closed and I haven't settled into a good routine yet.
For me it is a lot harder to hold presentations for groups remote than in person as almost all feedback is gone. Due to muting I don't even hear whether people are laughing at my bad jokes.
Recently, I switched from iOS to Android. And I was missing Apple's Continuity feature. Where I could easily make or receive phone calls on Mac, get access OTPs, messages quickly on my Mac. I noticed I was ending up landing social media or hacker-news :D spending hours every-time I picked up my phone for a call(there're a lot in this work from home situation).
And then after spending a day, going through a lot of spam! I noticed this app on App Store called "Connecton". I'm surprised why was it hard to find it.
Putting out loud, so that I can save someone's time who needs this.
I'm a college professor. Overall, working from home is alright, but --
I wish I could see my students' faces as I teach. I'm used to looking, and being able to get some sense of when my students are confused or annoyed. Now, the only feedback I get is that which my students explicitly choose to provide.