I started my daughter watching the films at 5 months old. This was in response to a mom who thought her brother (a HUGE Star Wars fan) was evil for letting her child watch Star Wars at age 4.
My daughter is not scared of anything and her favorite characters are Yoda, the Ewoks, and Jar Jar. We'll have to work on the Jar Jar deal though.
I remember when Star Wars aired on HBO back in the 80s. I was GLUED to that screen. And I was about 4. Star Wars is better than a lot of the crap they let 4 year olds watch..