I was booked on Mariner for an Alaskan cruise next year.
Last week, I got a brochure in the mail with a new offer from KLT - although I think the offer was pursuant to a new group booking by the Signature group - and these new fares were so much better, and the OBC available was so much more that I switched itineraries.
I don't have any links to share, but if anyone is interested, let me know and I'll expand on the subject. The group fares are less than you see on Fare Compare and the Regent web site.