The Star Wars Weekends are usually held from mid-May through the first or second weekend in June. We have been once in 2003 and in 2005. We're usually there for the last weekend. In 2003, the crowds weren't that bad. Most people were there for the SW festivities, so the attractions weren't crowded at all.
Last year was a totally different story. The park was VERY crowded. DS and I stood in line for 45 mins just to get into the SW store. We love SW. My DS (12) is a huge fan and the crowds didn't bother him at all.
I definitely think it is worth it if you are a SW fan. My son could care less about the cartoon characters now, but he loves seeing all the SW characters roaming around. Normally he is very impatient and hates lines...but we stood around for about 1 1/2 hrs. one day waiting for Darth Vader!! He never complained.
I would go ready to enjoy myself, but prepared for crowds. ADR's are definitely a must if you plan to eat in the park.
It truly is an enjoyable experience. I definitely recommend it for SW fans!!!