I think this is great news... PostgreSQL is definitively my favorite open-source database. It's also nice to see Amazon get into the game, as hosted pg options have been fairly limited. I am slightly disappointed to not see the server-side JS support baked in, and that apparently you can't do reads from distributed replicas. Just the same, I think there will be a lot of progress in this area.

Administering databases is a full-time type of responsibility. Yes, you can get pretty sane defaults, and up and running without much difficulty with MS-SQL, and mySQL has been a defacto standard in the LAMP stack. That said PostreSQL has been a rock solid RDBMS. The commercial extensions for replication have been cumbersome and expensive. Here's hoping that AWS will grow/expand the replications options/features, and that they'll grow to include JS procs as that feature stabilizes.