For Destin proper, we really like La Paz for good & fresh Mexican. I'm a sucker for their made to order black bean soup, and their prices are very reasonable. By far the best Mexican or Tex/Mex in Okaloosa County.
Osaka for Japanese and sushi.
Ciao Bella for Italian. Best thin crust pizza in the area.
McGuire's for American/seafood. Good year-round, but tends to be even better in the off season when it's only their core staff is working there.
Bonefish Grill for seafood. Yeah it's a chain, but it holds its own against the locals.
Quick bites- Publix subs; Panera Bread or Zoe's at Destin Commons.
Back Porch, Pompano Joe's, Louisiana Langiappe, and Gratzi are all owned by the same people. And IMO, tend to coast by on location rather than food quality. Decent enough fish, but cheapest possible starches. I'm picky about bread, and feel like the sandwich buns are sweet enough to taste close to cotton candy.