I had exactly the same experience with Karen Lewis as Bob K. She did refer my manuscript to her high-priced editor (on which I passed), but she was nice enough to critique my first couple of pages, and her comments were very detailed and helpful. As a result I've focused on correcting these mistakes, revamped the book, etc. The thing is she was the only agent who took the time to do so, and the impact was credible in my case. The lesson being: take what you can use, ignore the rest, and move on.