The food isn't fancy, but it's certainly an 'improvement over' what we're served at school.
His cooking needs 'improvement'. = There's still 'room for improvement' in his cooking.
The editor made some 'improvements' to/in the article before it was printed.
(..) -That's right. Take a moment. -I'm sorry. I don't know. -Six dollars an acre. Six dollars? Thank you, Eli. And then with the improvements to the ranch over the years at $... I'd like to offer you $ for this ranch. -That's $. -No. (..)2007 There Will Be Blood