Other than multi-touch gestures, full-screen mode, mission control etc main new features, Mac OS X Lion has numerous small features that make life just much simpler. It is now alot easier to access accented characters under Mac OS X Lion.
Just hold down the letter for a little more while and a list of alternatives accented characters will show in a popup. Press the number below the desired character to select the character and continue to type as usual. This feature appears in all apps that make use of Mac OS X Lion Cocoa text edting components.