Mine improved drastically (DP4) on a Retina MBP (2.3GHz / 16gb Ram).
Screen brightness @75%, iTunes playing in the background, web surfing, I get a solid ~6½-7 hours of battery.
With ML, it was a miracle when I could use this laptop more than 5hours on battery.
I don’t know if it’s good battery life or not for this specific laptop model, but considering I have a bunch of thing updating in the background for notifications (Facebook, Tweetbot, Mail, iCloud, Dropbox, etc.) I think it’s not bad at all.