I like the punch too. It also helps distract from Roys ugly hat.
For those who don`t know, it`s a technique that strikes at darkness that was created by Ducra of the All Caste, passed to Talia, who couldn`t quite do it (because she`s a Al Ghul, mostly) and from Talia to Jason, after he watches her doing it. This is the most Dragonball thing Jason ever did and is awesome.
It also serves to point something that a few writers, in their thirst for a Bat-Punisher tend to forget: Jason was never a rotten kid, even when he had to struggle with his anger. That`s also the reason Batman gives him a second chance eventually.
I love that it shows Jason's quick learning by observing. Fits well with his upbringing.