I travel for work and DH joins me for more than a vew vacations each year. We would never consider NOT using the Early Bird convenience.
The one word is convenience. We don't have to worry about being in front of a compter 24 hours piror to departure.....ESPECIALLY returning.
Even if you want to save the $$$ on the outbound flight, use it for your return and you will not have to stop what you are doing the last full day of your disney holiday to find a computer or guest services spot. Besides the fact that it might not be a convenient time to stop what you are doing.....we don't need one more reminder that it's our .... LAST DAY.
In addition....don't forget the frequent fliers on SW always get an automatic front of the line boarding number, now that "The Bird" has been up and running for a while now (and their numbers are chosen 36 hours out), don't forget that if you DON'T choose The Bird....you may automatically be behind a bunch of people before your 24 hour time even begins.
Now....add that to the possibility of handicapped passengers who board first (I seem to always fly with MANY of them to and from Florida destinations)....that pushes you back even more - added to all the other reasons listed above.
Ok, now....my cliff notes answer.....YES, "The Bird" is worth it for your peace of mind. If you don't mind the chance of not boarding early --- and don't mind the possibility of a center seat for your flight....don't bother.