Van Persie had his first training session at United on Friday.
Giggs told manutd.com: "He looks good. 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.
"The players are just like the fans in terms of talking about who we might sign and wondering which players might come in. It's always very exciting for us when we sign new players because you know that whoever comes in with have a lot of quality and will help improve the team."