I have a 25k certificate expiring next month and I always have always had a hard time using those as I mostly stay overseas where the rates are higher. I stayed a night at a Fairfield Inn last month while in the US hoping that it would use it, but it was apparently only 15k, so it just deducted the points instead of the cert.
Now with the flexible redemptions it seems like it could be even harder exactly hit the 25k so that the cert would be used and it would be great if it would (preferably) apply to a higher stay or at least let you use it for a cheaper one.
I just searched in my city and if I go tomorrow I can find one that is 25k, but then next weekend it drops to 20k. There is one crazy cheap hotel that is only 10k base, but you can point upgrade to a suite for 26k and that would be great if it would use the cert and then just charge me 1k.
Having to match the reward exactly to the price makes it such a pain to use that I don't even consider them to be a benefit and am probably going to end up cancelling that card.