That is something I agree with completely. The encore should be high energy - as in always leave them wanting more. An occasional ending with NSG is fine as it's their song. If they used this all the time though it would lose its punch.

I also don't mind covers as long as the original set was long enough and satisfying enough to want something different. Bon Jovi does some awesome covers - but they shouldn't be done at the expense of some of their best songs.

Put a surprise or two in the encore - many artists setlists are similar from town to town. Surprises at the end of the show will stick in the audience's mind longer than one in the middle.

Here is a good example of an encore from Bruce's show last night in Dublin:

Thunder Road - This is not played that much any more - a great way to open the encore
Bobby Jean - This is such a rarity that it is a big surprise
Born To Run - This is played at every show. Think of it as Wanted
Tenth Avenue Freeze-Out - This is also a rarity and a guest (SSJ) was invited to sing along as he was in town too.
American Land - This has been played at every show on this tour. It's a new song that was translated from the Seeger Sessions.

Now in my opinion - THAT is how an encore should be constructed. And not a ****ing ballad among them