[ceejayoz]

There are ways to non-annoyingly ask for a review.

Wait until the user has meaningfully used the app. Don't interrupt the user mid-flow (a banner on the dashboard, a call-to-action on a piece of existing copy) with a modal. Provide a clear "never ask me" option.

[kalleboo]

By App Store rules (5.6.1), you're not allowed to ask for reviews through any method other than the Apple modal dialog. This means you can't make it non-obtrusive or customize to add a "never ask me" option.

[ceejayoz]

I tend to doubt they'll reject a subtle "Love our app? We'd love to hear your feedback." that invokes the Apple dialog.

I've seen quite a few apps taking such an approach successfully.

[kalleboo]

They did for us. After having it there for a the better part of a decade. The luck of the draw with unreasonable reviewers.