I am not a big fan of United Cruises because of its agency booking fee and agency cancellation penalty , but there is a promotion (ongoing for a while now) that can get you United miles at 8x dollar spent. Thus, a $4,000 cruise would net you 32,000 miles (on top of the 4,000 miles you'd get by paying for the cruise with your United card). Speaking of which, you have to use a United Visa* card and book a balcony cabin or better to get the full 8x miles. Not booking a balcony or better will still get you 4x miles. Miles are posted to your MileagePlus account 6-8 weeks after your sailing.

Additionally, United Cruises will waive/postpone the cruise line's deposit (up to $500) for many cruise lines. Not Carnival.

*The cyborg to whom I spoke said I could use my Presidential Plus MasterCard instead of a Visa card, but I'm leery; the "rules" specifically state Visa card.

The foregoing is accurate as of today. Tomorrow? Who knows?

RNE, detailing the aforementioned agency fee and penalty: Agency booking fee of $24.99. Agency cancellation penalty of $100. These are separate from the cruise line's fees and penalties, which usually don't kick in until 75 days before sailing.