Nushield is rather popular although at notebookforums they seem to be love it or hate it. It does provide a layer of protection for you screen however it is also quite reflective giving it a poor-man's Xbrite look. The problem is that it looks like a mirror in sunlight or florecent lighting and can be super annoying.
Do a forum search for Nushield and you will find more info than you ever wanted. I have one on my Inspiron 8600 and I really like it but I can see why people hate them too.