Well, I have mixed feelings about it.
If you do it because there is no other place to work ( you work remotely, there is no coworking nearby, there is something wrong with wifi in your place), then it's okay. But I know some people who do it just because it's "cool", then sorry, it's not cool.
Sometimes I want to have a coffee and there is no place to sit because of people with their laptops. And some of them don't even work, just chilling, and it's annoying.
If the cade isn't crowded, it's alright. But if during peak hours people are enqueued to get seated, while plenty of tables are occupied by this, ahem, workers — nah, that's not cool
I typically have productivity spurs of about 2-3 hours. Perfect to order 2 drinks and some food.
Growing up with parents that had a restaurant I can see the annoyance regarding people who order 1 small coffee and stay for 7 hours, even if the cafe is empty.
So definitely a "make sure both parties benefit from the arrangement" kind of situation.