We've eaten at both Carrabbas and Outback. Steakhouses are among the easiest places for us to eat. Carrabbas doesn't have any gluten free pasta but they do have some really amazing food. I remember one time eating this fabulous scallop salad with some kind of home made vinegrette dressing and thinking it was just amazing. The chef really "got it" and even warned us against something on the gluten free menu since at that location they typically make it in the same part of the kitchen as the pasta so it would most likely have cross contamination issues. That really gave me confidence. Things really do vary by location though. I've read horror stories of Outback where they just pick croutons off salads and bring steaks out on garlic bread even though the customers have re-itterated many times that their meals have to be gluten and dairy free. I've never experienced anything like that though. We've had only good experiences at both. At a Longhorn Steakhouse one time, the waitress came back to the table to make sure I was ok with the fact that our steaks wouldn't have grill marks since they'd be cooked with foil over the grill to make sure there was no cross contamination from the grill. The same chef also said that he wasn't confident that the fries would be safe since even though they have a policy of a dedicated fryer for their fries which are gluten free, he wasn't sure about one of the guys on another shift doing the same so he didn't feel it was safe. Yup, that sort of thing gives me confidence. It's wonderful encountering these types of things.
The restaurants at DTD will accomodate you as best they can, but non-Disney owned restaurants just don't have the same kind of allergy safe alternatives on hand as the Disney owned restaurants do. They'll try and your meal should be safe, but you'll be limitted to maybe an unseasoned steak and plain baked potato like you would be at home. I figure when I'm at WDW I want to be spoiled by all the amazing things I can't get at home so I stick with Disney owned restaurants.