Is it worth it? There is a $20 difference between the regular version and shield version
http://insider.nike.com/us/shoes/shield-pack-running-shoe-358/
"The Shield Pack Collection is made up of some of Nike’s most popular men’s and women’s running styles, all with breathable, water-resistant uppers to help keep feet dry. Every Shield Pack shoe also has reflective elements for enhanced visibility in low light—ideal for late-night, early-morning or less-than-sunny daytime runs."