While it's nice to make a bit of cash from my apps, getting a good review is always great; I don't think many users appreciate how much effect they can have on a developer; a crap review (especially nonconstructive ones) can be a real downer. Even the most basic app takes days of work, and when they are given away free but a user still leaves a crude review like "this is rubbish", it makes you think "What is the point?".
Conversely, getting a good review is great and really makes it all worthwhile. Here's a humdinger that I received a few days ago for UK Traffic Alerts. I've taken a screenshot since it could well get superseded by (hopefully) just as gushing reviews.
Whoever Peter is, I thank you!.