There were requests for benchmarks of performance difference. Tomas has promised to run a couple of benchmarks on his standard benchmarking setups to give numbers on that. Thanks Tomas, please pipe in with your results when you have them!
Security considerations about pg_hba.conf -- I avoided those by not actually changing pg_hba.conf. Since pg_hba.conf can be changed on a reload instead of a restart it's a lot easier to deal with. I still think changing it to allow "postgres" the same type of connections as it does for regular users would not be a security problem, but again thanks to it only needing a reload it's not as big an issue.
There was the idea to have multiple sets of defaults to choose from at initdb time. I don't see a problem having that, but it's been another year and nobody built it. I don't think not having that is an excuse for the current defaults. And implementing something like that is in no way hindered by
changing the current defaults.
We were too close to beta1 -- this is why I'm sending it earlier this time :) (Even though I intended to do it already back in September, better now than even later)
Finally, there's the argument that we're already shaking up a number of other things with version 10, so this is a good time to do this one as well.