My own rescue has certainly changed - mostly for the better, sometimes for the worse!
He also came eating very low quality food, and was a little underweight as he didn't like eating it. Now he knows what the good stuff tastes like, he expects luxury as standard, and has been known to turn his nose up at other people's dog treats in the park.
He's learned that he can walk away from a snappy dog, and doesn't have to turn it into a scrap. He has always hated one breed, and added another to his list of breeds he hates for no apparent reason (we just avoid them). He also developed a hatred of motorbikes (now much improved, but probably as good as it will get), discovered the joy of rolling in corpses (today it was a frog) and has chased every squirrel in the locality.
He stopped raiding the kitchen bin multiple times a week, has learned all the usual commands, has decent recall, rarely pulls on the lead, his housetraining has remained solid, and he's perfect 99% of the time (and utterly horrid the other 1% - there's no inbetween).
He's become more territorial, and can get a bit shouty on certain occasions, but he's been taught that visitors = a game of fetch, so he's quite happy with them now.
One of the more subtle, but perhaps nicest differences, is that he now wags his tail a lot more. I used to think he just wasn't an especially waggy dog, but I think he's just a lot happier now. He also seeks affection from his nearest and dearest (he used to just accept it in small doses), occasionally asks to be picked up (wouldn't let you at all before), and will even occasionally accept affection from strangers when off lead (he's always just ignored / avoided their attention).
The current state of play is that he's much happier, I can live with the 'rough edges' he has, and we understand each other. He'll never be "perfect", but he's the dog that taught me the serenity prayer - in this household, it goes
Dog, grant me the serenity to accept the behaviours I cannot change,
Courage to change the behaviours I can,
And wisdom to know the difference
