Slipper- I think the fact that they got out quicker the second time was something to do with the fact that they had done it once, and had had a practice "shot" at it - the second time money was being offered, and so of course they got out quicker, plus they had already done it once- like you say, not very realistic. In a real accident, surely fear would inevitably take over, along with the mobility problems of the elderly and disabled hindering evacuation considerably.
Max Angle, they were offering £5 as an incentive to the first half out of the aircraft to try and simulate the instinctive rush for the doors normally caused by panic.
I also found it interesting that the "yellows" who had read the safety card and thoroughly and planned their escapes only made 16 out of the first 30 out.
G-BPEC