The synthetic ice skating rink is officially up and running in downtown Grass Valley to the delight of more than 100 participants who visited the rink Friday. “It’s definitely been a hit,” said April Halliday, volunteer for the Grass Valley Downtown Association. “We were expecting it to be slow since it’s a school day. This weekend is going to be nuts.” Some said the rink’s synthetic surface took some time to adjust to. “It’s not the same as real ice,” said Jennifer Roberts, who skated with her son, Holden. “It glides fine but doesn’t grip at all and you can’t …