Stay away from The Palm...it definately does not live up to its reputation.
Trattoria is pretty good for lunch, very good for Breakfast.
We have never eaten at Delfino...but the people we talk with while we stay there (other guests) really enjoy it.
You are also just a short boat ride from City Walk...over there, we love Emerils (make a reservation well in advance), and Latin Quarter (make a reservation here also). Both of these have great food and service. Of course Emeril's is very upscale and worth every penny...can't wait to go back.
For a great snack..we love the volcano nachos/shots/beer at margaritaville, yes, the margaritas also.
NBA city is also pretty good...but I would eat at the others first.
Also...for great quicker meals...even though they are not really restaurants...Pat O'Briens and Bob marleys have some excellent food/appetizers/sandwiches...etc...very very good.