Description of Sous-Vide

When I first started reading about sous-vide I didn't quite understand what advantage it had over other methods of cooking, I thought it was simply boiling food in a plastic bag. It turned out to be not that at all, a lot of sous vide cooking is done under boiling temperature. As for what the the main advantages of sous-vide are, this is one of the best descriptions (imo) that I've found so far, here:

Protein products have very delicate transition temperatures - which give you a narrow range between underdone and overdone. That is where sous vide has a large advantage over conventional cooking techniques.

So for example with a traditional roast the outside is overdone and the inside is underdone. With sous-vide you keep it in a water bath that is the exact temperature at which it is considered perfectly done, neither underdone nor overdone, until it's the same temperature all the way though, at which point it can be taken out or left there to dissolve connective tissues to make it more tender. No you don't get the nice crust on the outside but you can always add it after by several different methods, frying, broiling, torching, etc. and keep the perfectly done interior.