After having a rather "off" experience at Commander's a few years ago, my wife and I decided to give it another shot on our anniversary. We were not disappointed. The food was very good (the gumbo was meh), and the service was excellent. The drinks waiter accidentally began to put champagne we hadn't ordered on our table, and caught her mistake halfway. Very apologetic, she later brought us complimentary shooters of their mango rum cocktail (that was delicious).
Otherwise, the service was attentive, but unobtrusive. Some of the neighboring tables of several people did get a little rambunctious, but it was a Saturday night, and New Orleans, and we would likely have been as much were it not just the two of us.
Dress code: My wife wore a nice "going out" dress and I wore dress slacks, a button-down, and a jacket with no tie. We seemed to be in the average, with some dressed a half step nicer, and a few others in polos and khakis. In short, dudes wear your church clothes, but not necessarily Easter or Christmas nice (though you wouldn't be out of place if you did). You may feel uncomfortable in just polos and/or jeans. As mentioned before, shorts are a non-starter (despite the fact it gets stupid hot outside for much of the year).
In sum: Restaurants at that level all have similar quality food (with the exception of some signature dishes), it's the service that often distinguishes them. This visit to Commander's reconfirmed its reputation...but YMMV. The experience before (albeit years ago) was pretty dismal.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.