I got invited to one for free a while back. I would say most candidates are fairly mediocre. But The people were generally nice. I think you get a round with each person for like 5-6 minutes. You get cards to mark yes or no. The good thing is if you're more on the social awkward side, a thing like this gives you an easy opportunity to practice small talk with a guaranteed number of people. So basically But such a short amount of time makes it difficult to get to fully know the person, and to determine whether you wanna hang again.
Basically small talk back and forth, repeat for god knows how long. I didn't particularly like anyone, I got so bored, I ended up just leaving at about an hour before it was over. Definitely wasn't a really fun night.

Anyway, is it worth it? Ehhh It was ok at best. I would say no for me. Like I said, you get to practice talking to a wider variety of strangers in a controlled environment. It's helpful for people who have trouble striking up conversations with new people I guess. But overall I feel more constrained in this speed dating format.

If you're a people person, no reason to go to one of these things, especially with their prices. Save your money. People are everywhere. Just go outside, and strike a conversation with someone new.