Anti-glare films vary greatly in quality and price. Some films introduce color shifts and artifacts which detract from the user experience.
I have the $35 Power Support anti-glare film on an iPad and 13" MBP. It isn't the cheapest but it is high quality. When I compared my 13" MBP to my 15" MBP with Apple's matte display I could not see a difference between the two displays.
http://www.powersupportusa.com/accessories/macbook-pro-13/anti-glare-film.html
I'm typing this outside under a patio umbrella in full sun with no annoying reflections.