There are many benefits to subscribing to a series at the Hollywood Bowl. One of the best is getting to purchase tickets to additional concerts before the general public. This usually guarantees great seats to Opening Night, July 4th Fireworks Spectacular, Movie Night, Sound of Music Sing-a-Long and others.
If you are a current season Subscriber you had the opportunity to purchase tickets before the Holidays. If this will be your first year (subscriptions for the 2013 season available for purchase starting January 29th) there will still be great seats since general public sales start in May.
A complete list of subscriber benefits can be found here.