Eh, I wouldn't, but I know people who have tried them and liked them. I wouldn't mind trying one of those atheist "churches", but I don't see myself going regularly.
Honestly, the only thing I miss from church nowadays is the community, and I've got a circle of friends that meets that need now. We get together a few times a year and basically party for two or three days. We also support each other when one of us is going through hard times, whether that means helping someone pay their rent when they've lost a job or just giving someone a shoulder to cry on. A lot of nonbelievers form groups on social media sites to build similar communities.
Some people who have left Christianity miss going to a formal service every week, so going to a Unitarian service (or something similar) helps them cope with the loss of their faith (which, as I've said more than a few times, can be a pretty difficult experience). Personally, I was never crazy about getting up early Sunday to go to a service outside of the social aspect, so I probably wouldn't bother going to a Unitarian service. But if it makes people happy, more power to 'em.
A vegan atheist walks into a bar. Bartender says "Hey, are you a vegan atheist? Just kidding, you've mentioned it like eight times already."