I've definitely had apps reviewed on AppAdvice and not seen a dramatic bump. I think it really depends on the app, what people are currently buying, and a lot of other factors. On the promotion part, I totally agree. What's worked for me on that front is to make friends with people in the press (on twitter, IM, email) way before I need articles written so when I need press it's really easy to get written up because they already know who I am.