(You don't write yourself, or know much about the technical part of writing, but you're an avid reader with a general sense of what is good and bad).
Personally, I've had all different kinds of critique partners. Let's just say I have a few notches on my CP Bedpost! Right now, I've got some especially awesome CP's rollin' around in the bed sheets with me! Wait, too much? Sorry.
But as for me...I would call myself a Big Picture Brainstormer. I wouldn't say my strength is in grammar or coaching voice. Not. At. All. In fact I hardly ever draft the correct version of contractions, i.e. wont, dont, your, their. I know, not awesome for an attorney who drafts very important legal documents (spell check is my best friend). No, I like to hit the major plot elements. I like to strategize and strengthen the ideas.