Red Lobster is a chain and I would say is to seafood what Pizza Hut is to pizzas. We haven't been to one in Orlando, but we did try one near Charleston a couple of years back. Of its type, it isn't bad, but it probably helps to understand what you'd be experiencing - you wouldn't need to be donning your finest togs.
We really like McCormick and Schmicks (we've been to the Mall at Millenia location several times. There's also one at Winter Park.) It doesn't always get the best reviews, but I think some may be misinterpreting its position in the market. I wouldn't say its aiming to be a top-end place. It does have a very smart, 'expensive' look, but the prices aren't offensive - we find we don't pay any more than we do at The Cheesecake Factory next door. Due to its location, we tend to go at lunchtime and it's usually full of business people. Whilst no-one would bat an eyelid, you might feel a bit out of place in shorts and a t-shirt.
I've heard good things about Dixie Crossroads at Festival Bay, but we've yet to try it. My impression is of a casual eatery, but, by all accounts, the seafood is top-notch.
We absolutely love Ruth's Chris. As others have said, this is an upscale place and isn't cheap. We've eaten at the Sand Lake Road location several times - its unassuming exterior (in one of those strip-mall places) totally belies the opulence within. That said, it's not stuffy, but you would want to dress up a bit. The steaks are cooked in 1800 degree ovens and are sublime. They come dripping in butter, which I like but dh doesn't. If that's not your thing, ask for yours to be served without. They also do some delicious sides, but don't be tempted to order too many - the steaks (even the filet) are huge.
Another favourite is the Old Hickory Steakhouse at Gaylord Palms. Again, not cheap, but really good food in unique surroundings (the restaurant is in the Everglades themed area of the hotel and is styled along the lines of a shack).
Salt Island Chophouse and Fish Market does a good job of being both a steakhouse and a seafood restaurant. It's a bit incongruous in its location on I-Drive - its a stunning place and one to which we'll definitely return.