I think people may be overanalyzing the $$ vs. points in the survey. It may be that there is no intent at all to have a sliding scale program, but instead they're trying to give a range of responders a range of tradeoffs to get a more accurate estimate of how much people value today's 1 RR credit, and how much they value other new perks such as guaranteed better boarding passes without waiting for T-24.
I know I don't buy BS fares for the extra .25 (I don't fly WN on routes long enough to qualify for the 2 points for BS). I don't even buy BS fares for the exit row, although it's a nice bonus when it happens - I usually end up in 14 through 16 C. I buy BS fares over Anytime fares because I know I'll get an aisle seat, and I don't have to worry about remembering to check in early. So, we've proven that I'm willing to pay $15 for that, just like I'm willing to buy-up to an exit row for $15-$20 when I occasionally fly Northwest or AirTran.
But is it really $15, or is it $20? That's what I think Southwest is trying to find out with this exercise.