If the app is useful to you and it is free and not inundating you with ads, a positive review is the least you could do in return. It seems reasonable.

Unfortunately, it doesn't change the fact that users hate it.

The question is if they hate this enough to actually go and rate the app, but give it a negative review. And I don't think they do. Those who are ticked off would simply not bother rating, so no harm done by asking.

Appirater defaults to asking only once, and not until two weeks of steady usage. This helps get better reviews since people who use the app a lot tend to like it. In addition, developers have full control over when to display the prompt to avoid interrupting certain tasks.

If the developer implement it the right way, choosing 'no thanks' will stop asking for reviewing. In addition if it's implemented the right way it will ask once in a while rather than every time. I have implemented such request to review in different applications in the AppStore but so far the result is pretty mixed: some app got a few extra reviews, but others none with apps being the same quality.