And you're starting with a Half...
You will enjoy them. Expensive, but worth it. Character photo opportunities in the parks and along the course, photopass photographers everywhere it seems (photos are included with registration), bands, cast members cheering you on, 1st aid tents and EMTs on bikes following runners if medical help is needed, water stations every 1.5 miles, a fuel station around mile 10 (hand out gel packs). My issue - not enough porta potties. Lines are long...and runDisney is serious about sweeping racers who can't stay ahead of the Balloon Ladies.
Once you finish your first, you will want to sign up for another!