I love it. She is this beautiful actress, one of the biggest names in hollywood, and when she laughs she just lets it all out, holding nothing back. It's loud, and it makes me smile every time I hear it. Anytime I hear it in a movie or in an interview, it makes me smile (can be heard most recently in the movie Valentine's Day)
This clip from the bloopers of Pretty Woman has a great sample of it right at the first.