It's going to be very different. You just need to remember that it's not what you are used to and try not to compare, even though that's difficult. I think you'll have a very good time.
Jazz Kitchen was a favorite of many, not just the food, but the atmosphere. It was remodeled and turned very bland. I haven't eaten there since it reopened, but it doesn't look "fun" like it used to. Someone who loved it before probably wouldn't like the changes, but since you've never been there, you'll probably be fine if you like the menu.
I eat mostly at the hotels and I am extremely picky. I don't like theme park food. You might enjoy the Craftsman Bar at the Grand or the Palm Breeze Bar or Broken Spell Lounge at the DLH. Those places all have good food and are just a few steps from Downtown Disney. Of course, it all boils down to what you like to eat and how much the atmosphere is going to matter to you.