"He who marches out of step hears another drum." ~ Ken Kesey
I've done the technique in Illustrator but like Will35 said, it's not totally accurate. About as accurate as using photoshop to match a CMYK color and it gets to close but sometimes it's way way off.
Lets not forget the Pantone Bridge book is also available. . . It's not on the web, but I like using the book as you can look at may pages at the same time.pierre