I just flew BS the other day, but only because the Sunday Thanksgiving fares were blocked out for anything less expensive than the Anytime fare. Because of this, I figured it would be worth the $15 in terms of time saved and the drink - I would have been looking at a C boarding group otherwise on a completely full flight. (I don't care much about the credit because it's only 0.25.)

In general, though, I wouldn't value the BS fare at much more than the difference between that and the Anytime fare.