I liked this chapter and I'm glad that the author isn't rushing the story. This is a huge climax. It would be a total letdown for me if Clare was able to actually challenge Priscilla at this point. Although I've been disappointed by authors before, for now I have faith in the story's direction. And I felt that there was progress. I liked Clare's decision to awaken, and her subsequent inability to do so. The plot did move forward some.
Regarding why Claire can't transform, I think it goes back to her being unique amongst the Claymores and having Teresa (that is, another Claymore) inside of her.
I honestly have no idea what's going to happen in this fight. On the one hand, I'd like to see Clare have a revelation that lets her fight Priscilla a little more effectively... But I feel that the author has something more clever and dramatic in mind.