Bought an 08 Impala SS a few weeks ago, really enjoying it. Nice big car, comfortable ride, lots of power, I think it looks great. Quibble are lousy interior lighting (almost impossible to read a map in the front seat at night with the small lights in the rear view mirror), and odd cup holders; seats a bit flat. Easier to get into than my 06 Grand Prix GT, and easier on fuel too. It's your grandad's Impala until you stuff your foot into it.
Engine, for sure.
Better interior lighting, better designed cupholders, little more supportive seats.