It must be me. I really liked Stephanie as a supporting Bat-verse character, as Cass' best friend, as Tim's girlfriend, I even liked her as the spunky Robin who was unaware Bruce was just using her to teach Tim a lesson. But she doesn't seem like a Batgirl to me. I just don't think Miller can convince me there's a reason for her to be Batgirl other than just because DC Editorial says so. Gail Simone posted at her YABS board awhile ago that Charlie/Misfit almost became Batgirl in the early talks, which would have been disastrous but only tells me the fact that Stephanie is only Batgirl because she's a known Bat-verse character who's not "radioactive" thanks to bad storytelling(like Cass), she's not, like Babs, disabled and as old as the woman calling herself Batwoman (I hate to put it that way, but honestly I never thought Babs was going to walk again after all her years as Oracle and why would she call herself "Girl" anything after all these years) and she's not a meta-human with powers which would make her stand out like a sore thumb in the Batclan (like Misfit).
So Stephanie wins the title by process of elimination. Which works fine in an editorial meeting but not so well when you have to explain to jaded readers why she suddenly is "Batgirl". Just because Tim told her to stop wearing the Spoiler outfit and Cass dumped the Batgirl one is not a good reason. And I also hate Babs is again demoted to a "mentor" role - as if she didn't carry her own book for over 100 issues. But like I said it's probably just me.