come a long way
To make significant progress. Almost always used in the present perfect tense ("has come a long way," "have come a long way"). He can play entire songs now, and they sound pretty good! He's really come a long way from when he could barely hold a guitar.
come a long way
Make considerable progress or improvement, as in That's good, Rob-you've certainly come a long way. This usage, which transfers the "distance" of a long way to progress, gained considerable currency in the 1960s and 1970s in an advertising slogan for Virginia Slims cigarettes addressed especially to women: "You've come a long way, baby."