I previously had a Worldpoints card through MBNA before they actually called in Worldpoints. When MBNA increased their point requirements and lowered their maximum allowable fares I dropped the card and converted to their Amtrak card which allows you to earn miles in United and Continental; however, they are capped each year. The cap does not bother me becuase my primary card is the Starwood AmEx which I feel provides the best earning value out there despite the poor level of service from AmEx. I only use my MBNA card as a back-up where AmEx is not accepted.
With all of that said, I decided to switch back to the Worldpoints card next month instead of using the Amtrak card for a few reasons. I will still be using my Starwood as my primary card; however, I have been finding that it is becoming more and more difficult yo book airline award tickets due to blackout dates. I like the flexibility that Worldpoints provides in that they will use any airline that has an available seat. To be honest with you, I have more frequent flyer miles than I know what to do with (not really) so my goal is hotel points. MBNA is extremely flexible with hotel stays uisng points. I have stayed at Hiltons when Hilton awards were blacked out through HHonors. They also obtained a week for me at Disney World in their Animal Kingdom Lodge. The nice thing about Worldpoints is that you can still earn frequent flyer miles or hotel points on your flights/stays.
You indicated that you were interested in the MBNA card primarily for airline travel. I have only once used those points for airline travel. As someone previously mentioned you do not have the option to choose the airline. MBNA books you on the lowest fare; however, they are somewhat flexible with times of travel so I was able to book the flight that I wanted.
The last time I redeemed points was when MBNA contracted with Carlson Travel. I do not know if they still use Carlson, but if so the rep's are fantastic. Some of the rep's do not like to play games with discount codes for hotel stays, but some go well above and beyond the call of duty.
If you can live with their dollar caps on the awards, I would highly recommend the card. Again, I still use my Starwood AmEx as my primary card, but the Worldpoints card is a great back-up.