I wouldn't say it's entirely dependent on reading Generation Lost, but it does cross over a fair amount. 13-25 might stand fine on it's own (haven't read it in awhile) but if you're cutting back your reading list then your money is probably better spent elsewhere.
I'm almost done with the last trade and I have to wonder, did they ever do anything with Rahan Mazin's character?
"A fast low flying Power Girl could take out a platoon of soldiers without even throwing a punch."
-someone on the DC forums
Let me point out here that Power Girl is part of the new digital-only Ame-Comi Girls comic book out in May on Mondays, thought the art isn't by Connor, who does Wonder Woman for that series. It is a weekly 10 page thing with all stories written by Palmiotti and Gray.
And here's a link to check out Mike Bowden's art:
Pants be damned! This could be pretty darn cool. And new Amanda Conner art is always worthwhile, even if it's not on Power Girl.
"I want to see beautiful people doing amazing things." - Grant Morrison