That might sound like a cliche and it is but poor updates reinforce it.
The New 52 is doing things differently and not worrying about continuity (unless it's Batman or Green Lantern) for the sake of fresh air and mostly for new readers. So new readers might found Power Girl interesting if only for the eye candy. Gerry Conway & co. however did a lot of things right when first introducing Power Girl in the 70's. Here's a few examples:
A Good Characterization - People might laugh at this but Karen Starr has a distinct voice, especially in her 70's debut. Whether you like or dislike the feminist tone PG was a force to be reckoned with. She wanted to be the best and saw pretty much every male as her competition. She raced Jay Garrick, she bantered with Wildcat and the Star-Spangled Kid, she took over from Superman who made her a JSA member. This got Karen all emotional and she cried when Star-Spangled Kid seemingly died. So even with PG's bitchy streak she still had heart.
New 52 - Karen is essentially a bimbo who isn't afraid to flaunt herself to pretty much every man she sees. While the old PG didn't have a problem with men ogling her she didn't dress or behave to get noticed by them. The new Karen seems to be enjoying herself more as a celebrity being on the covers of magazines or mingling in high class social parties. Karen comes off as shallow and vapid when the original character was supposed to be a no-nonsense career woman.
Distinction To The Superman Family - Power Girl differentiated herself to her kryptonian cousin and the Supergirl of Earth 1 with a few simple yet effective ways. Like Supergirl Power Girl had promised Superman to remain hidden from the world. Unlike Supergirl PG stepped in the limelight when the world was in danger. She introduced herself to The Flash and Wildcat and the trio started to work together. In a later story the Star Spangeled Kid uses his Cosmic Converter Belt to make an emblem for PG. It turns out to be the Superman emblem but with the letter P instead of S. Karen crushes the emblem and explains she is her own woman and not a carbon copy of Superman.
An Iconic Costume - Any publicity is good publicity is another cliche and PG's costume, or a certain hole in it has got people talking. That's not the reason I think it's overall a brilliant costume. I like how the cape is attached (underneath her arm). You hardly never see such a distinct cape design. The coloring (white, red, blue with a bit of gold thrown in) works in harmony and hasn't dated one bit unlike her other golden and Atlantian blue suits.
New 52 - Karen starts out as Supergirl and even dresses similarly to Superman who seems to be more of a mentor figure to her. I don't mind the relationship but something is clearly lost with Karen not being as independent as her 70's counterpart.
Granted, Karen is now a falling star (quote from a magazine cover) who is now facing some realities of life. Power Girl is also back in her original costume but even that is kinda screwed up. Karen gets her new costume from Supergirl's Fortress. The costume was meant for Supergirl and she remarks that Karen is too old for a costume like that. Again, the reasons that make Karen Power Girl are just kind of given to her as a result of pandering to fans instead of making the transition an organic one or rooted from the character.