A plain pan creates a better crust and flavor on the surface of food. It also creates fond in the pan for use with pan sauces.
A plain pan can be safely heated to HIGH temperatures for searing with the above mentioned effects. Teflon outgases toxic fumes at high temps. Some people claim other dangerous effects with coatings (most are teflon based) at lower temperatures. And regardless of coating, any scratches introduce the coating to your body through the food. While that is claimed to be safe, it's not really known and probably wise to avoid.
Most food will release itself pretty well from a plain pan when it's done and ready to be turned. The main violators of this principle are eggs, fish and starches. They too will usually release when well cooked, but that's not always what you want. Cooking in generous fat can solve even those problems but may not be appropriate healthwise.
For those sticky foods many cooks do choose a non-stick pan and baby it beyond belief to protect the integrity of the coating and use it at medium and low temperatures only.
The other alternative is cast-iron. It won't be non-stick from the start, but as you develop the patina over time, it rivals non-stick and cooks extremely well. Cooks very well at high heat too. Cast iron has a bit of maintenance work involved, but it is minor. And it's not well suited to acidic foods (tomatoes, wine) that simmer more than a few minutes unless it has developed an awesome patina. Even then, it's wise to season well after those acidic cooking sessions to keep things working well.