Definitely good for marketing. You can pay to have your page displayed on other people's Facebook pages. A catchy profile picture makes a huge difference. People will like a page just for the profile pic, which gets seen by all their friends. No real negatives I'm aware of since any negative comments can be deleted by you.
FWIW I'm much more concerned with being a presence on Google. Hundreds of people a month get directions to my wash just from people asking their phone "car wash near me."
That’s true but I really hate the reviews on Google. It seems we’ve had a string of ridiculously stupid comments which you can’t really do anything about. Supposedly our touchless wash has caused swirl marks, paint chips, and scratches. Believe it or not we also ‘ruined wheels and a custom paint job’ on a guys Aston Martin. Idiot dried his whole car with cheap paper towels that he dropped on the ground and also used to clean the brake dust off of his rims with. You can respond to the comments but you can’t post pics.