Some of these (like the one genuine Schwinn I have listed in the for sale area) are quite good, nice tight joints and good geometry. Some, like the cheap, Chinese repro that I have on my daughter's bike (it will be in the for sale area soon) have loose joints and aren't very simetrical. As long as the headtube length is right (kinda hard to change on these, as opposed to a regular fork) it sill fit. They're usually made for balloon tires and will look fat with a skinny tire in them.
For off road riding, they're great. For on road riding, they kinda get bouncy, like the same bounce as your cadence. That's why I'm selling mine. I don't get off road much any more.