Ever heard of adequate response? No? Well, in this case it would be writing a review about the app being nagware. In general adequate responses are good because they prevent situations from escalating into hostilities. Yours also has a sideffect of making it impossible for any buyer in the app store to make an informed decision, and therefore makes it hard for good apps to stand out on the merit. It ends up giving a boost to the actual crappy apps because now, with your generous help, all apps have bad reviews - both truly bad apps and the ones that had the gall to ask for your opinion.

It only asks once per 30 days, and only IF you used it at least 15 times within those 30 days.

Actually, it'll do it just once per version and only after 30 days and 15 launches. So if they tap 'Rate' or 'No, thanks', they won't be bugged anymore unless they update to a new version. Even then, only after 30 days of usage and 15 launches (which are both customizable).