We have used aRes Travel for tickets in the San Diego area (Legoland, Seaworld) in 2010 and for DL in 2006 and never had a problem. We bought our DL parkhoppers for our upcoming trip (10/20-10/29) from Ares because they had 6 day parkhoppers and a lot of the other discount sites only had 5-day parkhoppers. They sent us a "ticket voucher" that we have to take to a ticket window and exchange for tickets rather than the barcoded tickets that you take straight to the gate. I figured it was worth the hassle of exchanging the vouchers since we will have time to do it the evening before we actually want to visit the parks.
Thank you for the responses! Their park hopper ticket prices are less than Get Away Today, but I wanted to here from others experiences before I purchased them to be safe.
I cannot believe that our trip is less than 2 weeks away! Squeee!