I like getting the reactions too, Kelly - it makes me smile. When I review, depending on the story, sometimes I review as I go (usually if it's a long chapter, so I don't forget anything) and put in my reactions or parts I really liked, like Mare said. Othertimes I just review after I finish reading the whole thing and just give a summary of what I liked. And sometimes it really is hard to find something specific to say, even if I did like the chapter, but I figure anything is better than nothing.
Also, for anyone who gets shy about giving feedback, just know that no matter what you say or how you say it, as long as it's something positive, the author will appreciate hearing it. There are no stupid questions, and there are no stupid reviews (except for flames LOL). If the author doesn't appreciate it, then they're not worth your time, but most of us do.