We have had 2 bad encounters with the free DDP, both in 2005.
First one was at the WCC. The waiter asked us if we were on the DDP. When we said yes, he said "oh great, another table on the dining plan". Now I understand there is a lot of kidding around in that restaurant, but believe me, he was NOT kidding. We felt terrible as he was quite loud and rude about it. When he came back, we asked him what was wrong with customers on the DDP? He said that the tips show as income and he didn't used to show tips as high as he received on his taxes. My dh said later on (in our room) that it was a darn good thing that he didn't work for the IRS because he would audit him instantly. He made me feel so sorry for him that we left him a huge cash tip. Not only that, but every restaurant we went to after that we left a big cash tip on top of the DDP. Hello, stupid me. I would hardly complain about an 18% tip, even if I did have to claim it on my taxes.
The second time was at Capt'n Jacks and it didn't have to do with the meal or service. It was the table in front of us. I guess since they didn't have to pay for the food, the one lady got good and drunk and felt the need to SCREAM at my ds talking about someone being sick on the bus on his school trip (he was a 13 year old boy for pete's sake - vomit was a favorite topic of conversation). She was SCREAMING as him so loud the entire restaurant was staring at us and her. I was so stunned I didn't know how to respond, so I said nothing, just stared at her with my jaw dropped. She said she had lost her appetite due to what my ds was saying (PUH-LEASE - and may I add, WHY was she listening to our conversation anyways). Anyhow, they recredited the entire table theirs FREE meals that they ate 75% off, even her alcohol just to get her out of the restaurant. I was so upset that I couldn't eat a bite of my meal, and even though they credited it back, I was the only one who couldn't eat, so it was never used anyways.
Other than those 2 meals, we enjoyed the free DDP. It will be interesting to see how it works out for us this year.