I wouldn't say improved personally, they did take away the Shelby Series One's nice sounding stock exhaust and apparently the Boxer sound on the older impreza's too.
Now to say if all the cars have had sounds tweaked, I'm not 100% sure about that either.
Don't get me wrong though, from what I've heard about about the RUF BTR and Yellowbird they have improved them quite well over the previous sounds.
Some are good, some aren't so good.
True about the old Imprezas. I've been driving them most before and after the update and the exhaust tones sound fuller, but more muffled. I use the interior sound option with headphones exclusively.