Spending-based earning plus cash price-based redemption = totally boring. FTers would dislike it for that reason alone. However in the long run boring may look good when compared to treacherous, and that's where things are moving with legacy programs.
Virgin America, Southwest, and now JetBlue seem to be thinking very similarly on price-based earning. I understand some of their thinking on it, and I hope they understand some of ours.
I think that the appeal of spend-based programs is their simplicity to the non-obsessed traveler. The numbers are very easy to understand and there aren't issues with blackout dates. Lots of folks will love that for the simplicity and pretty much ignore that they are getting hosed on total value. Why? Because they don't care as much about the total value and never really actually realize said value anyways. For the mileage obsessed, however, the inability to game the system to redeem high value rewards on low spend earnings sucks. We are in the latter group for the most part, but the majority of the population is not. Legacy programs are skewed in favor of those willing to invest a bit of time and effort to manipulate them, making them appear to the general public as overwhelming and impossible to use.
So I completely understand why jetBlue would look for simple and easy rather than complex and fun, but it won't attract me as a passenger at all.
Oh, and it also means that folks who are used to redeeming for Caribbean and other "fun" destinations may end up losing, too, as those tickets are generally more expensive.