When I was trying to find my confirmation code for my VS flight (booked via Delta), I didn't want to sit on hold for two hours so I tweeted Delta asking them where to find the information. They never responded, but VS (and they were just mentioned, not @ in the tweet) replied for them.
I was very impressed with VS in that respect, but I've found Delta on Twitter to be slower and less enthusiastic since I first started communicating with them that way.