Think of it as pop-up from 2D like you find from children's books.
If you do go down on the smart tv line, be sure to test the boot up time and the latency when switching channels (or any command for that matter). I've seen smart tv's that take longer than the warm up time of old CRT TV's which can be just downright annoying. You may not think this is an issue initially but I've personally known people who threw out their tv's simply because they could not bear on waiting for their TV to finish the boot cycle.
Check what inputs you might be using if you don't have a amp/switch
Make sure wifi is certified as N standard, streaming high def content over G is possible but I wouldn't recommend on that.
Stay away from plasma unless you know what you are doing. Otherwise you'll end up with a large heater in your room. I'd say a large majority of LED tv's have decent contrast ratio and brightness, check the black levels if you are concerned.