Hi,
I'd like to suggest a little enhancement to the documentation chapter about file-system backup
http://www.postgresql.org/docs/current/static/backup-file.html
As I regularly see people copying files between different operating systems, I think it would be a good idea to add a third restriction to those listed on that page: that a file system backup will only work between the same OS and architecture and is not suited to migrate between different types of systems.
Regards
Thomas