Over the last 3 years i had been waiting for DC to bring Power Girl back, not the current 'New 52 Supergirl of Earth 2', but an actual Power Girl more akin to the old DC universe one ( you know, the smart, witty, but mildly short tempered and at times uptight version who had existential issues, never used the Supergirl identity, had a cat that was once kidnapped, carried a bit more muscle, was taller and had a fondness for direct approaches in combat. Oh, and generally wouldn't be seen wearing the 'S' shield or a variant of it unless it was on a T-shirt ). But it isn't happening, and it looks increasingly unlikely it ever will.
The differences between the Modern era Power Girl and the New 52 Power Girl are quite marked now with an origin at last provided for the New 52 version. At the very least it explains why her personality is so radically different, but ultimately it kind of obliterates what made Power Girl who she was.
Looking at the origin of the New 52 Powergirl, she left Krypton looking roughly about 5 years old, right after forming a connection/bond to the same age Val Zod ( Earth 2's current Superman after the original fell to Darksied ) , her ship arrived on Earth without her aging much and she was raised in an apparently very happy manner by an adult Superman and Lois Lane. She went on to adopt the identity of Supergirl when she reached her teens. She would never have even used the name Power Girl if she hadn't found herself trapped on an alternate Earth, one that she was desperate to get off to find her way home.
She -eventually- adopted a costume like old DC Universe Power Girls, but she is pretty much Supergirl ( with even the near exact build of Supergirl when they meet, with nothing to tell them apart other than hair style ).
In contrast, the old DC Power Girl left Krypton as a baby, and was raised in a 'Matrix' style computer replica of Krypton while she slept, her unique symbioship arriving on Earth when she was aged around 19 or 20. Finding that the life she knew was a computer generated lie, she pushed onward on her new home of Earth, met her now much older cousin Superman ( they both left Krypton as babies but his ship was much faster ) and with her notable independent streak assumed the name of Power Girl for her Superheroics to forge her own path rather than sit in his shadow. A year or two later ( in comic time not real time ) a multiverse crisis resulted in her being on an alternate Earth ( the main DC Earth from 1986/7 to 2011 ) with her memories in flux. At this point she was told that her previous memories of being a Kryptonian on Earth were just as false as her life on the Symbioship generated Krypton, and that she was an ancient Atlantean Princess, only for much later to be told that this was also a lie and that she was in fact from Krypton. In spite of all this, her response was always pretty much to outwardly dust herself down and push forward.
Basically, Power Girl has always had a certain amount of existential angst and doubt behind her smile, eye rolling, and outward confidence, ( and this is in part where her temper probably would come from ), and it was something that Supergirl never suffered from. Yet this has been thrown away in the comics, and with this and everything else stripped from the character ( that had developed her into someone interesting ), what is left is not Power Girl.
And the sad thing is this is not seen as a bad thing by some. Although i doubt they were fans of the old DC character anyway.