Probably everyone who can afford the money will be retaking it again and again till they get >80%.
Any comments on this new scoreselect option?
Well, you're kind of limited by the fact that the subject exam is only offered 3 times per year, and some people re-take 3 times anyway, sometimes more. I'm not sure that it's really a huge difference. If I were on an admission committee this might cause me to devalue the test as a legit measure of ability (not that other factors haven't already devalued it). This may be good for those who don't have great scores since it essentially takes information about performance on the test away from admissions people. Conversely, this might hurt those who get a great score the first time, since it would not be possible to distinguish between a once-and-done and a long slog of incremental improvements.