First thing to point out is that this is a measurement of how people think he is doing, not how he's doing. I'm sure everyone is aware of this, and it's a minor quibble with your subject phrasing.

Second thing to point out is that when we have an emergency, and our CinC doesn't screw up much, his approval goes thru the ceiling, no matter what.

Third thing is that in my opinion, it's generally a good thing for our president's rating to be high. This shows up in all sorts of unexpected places like: consumer confidence, more favorable stock markets, better executive/legislative relations (some major counter-examples here, but I think that in general, it's true). People who fret when a pres from the other party has high approval, probably deserve their ulcers.

Fourth thing is that as far as craw-sticking over approval ratings is concerned, the Republicans pretty much cornered that market during the Clinton administration.