I found this post here back from 2011, and wanted to verify that it's still valid and good advice to take a hot snapshot of an ebs volume (PostgreSQL still running) so long as you're snapping all of the data.
The PostgreSQL documentation indicates that a low level snapshot is fine so long as the whole data directory (WAL and all tables, different tablespaces could cause an issue) are taken in the same snapshot.
I'm currently using PostgreSQL v9.2.