Standish: If the nitrogen cycle isn’t established within a certain time, nitrogen will be removed from the atmosphere and the surface will become rich in nitrate (bad) or, in a reducing atmosphere, ammonia (really bad). The bottom line is that there are speculations that probably get around this, but it is one more needle that has to be threaded for chemical evolution to produce the first life, or a problem for the first life to quickly take care of.
Timothy Standish: The authors seem to have found that if you already have alleles that adapt you to a certain set of conditions, then you will be able to rapidly adapt to those conditions. The speed is impressive, but you could argue that the speed with which natural selection can work is not the real question. The real question is, “How fast can those alleles that make organisms more fit arise de novo in a population that doesn’t already have them?”