Programming language experience matters very much. Not least of all because it takes time to become accustomed to that language's idioms: Until you are fluent in them you are going to take longer to read others' code, you are going to write code that's harder for others to read, and thus you are ultimately writing code that is harder to maintain. And unless you are a very meticulous tester (and none of us are nearly as good at testing as we want to think we are) you are also going to write code that is more buggy because you are less aware of the quirks and gotchas that motivate many of those idioms.
