Van Persie completed his move from Arsenal to United on Friday and trained with his new teammates.
Giggs was impressed with what he saw of the 29-year-old in his first training session with the Red Devils and believes that the Dutchman is a valuable addition to the team.
"He looks good," the Welshman told United's official website. "You can see just from one training session the qualities he has which we know all about anyway because of all the times we've played against him.
"He brought that lift to training that a top player brings and that all bodes well."
Giggs further expressed his delight in having Van Persie at United.
"His movement is so good and he's got a real presence," he said. "He's big and strong with a great left foot and he scores all types of goals – poacher-type goals, goals from long distance, free-kicks, penalties... he's just an all-round top player.
"And he's improved so much over the last few years as we've seen by his performances and his goals."
United will begin their Premier League campaign with an away game against Everton on Monday.