I don't think the rating has all that much effect really. I can't remember the last time I looked at a rating or a review prior to downloading an app. What it does do, though, is ensure that the app is down the charts when "browsing" through categories.
I think the more concerning thing is that 25% of reviews are 1 star. That's a lot.
I don't have the app, but most apps these days will give you a reward for putting in a rating. Perhaps Divan could do something similar - 3 days free or something if you submit a review?
TV2 Price at posting:
2.7¢ Sentiment: Buy Disclosure: Held