upgrades and streaming replication

I just wanted to check if there are any updates on the preferred way to upgrade a group of servers that are using streaming replication with minimal downtime.

Mailing list messages from a year or two ago pretty much state the following:

* No current plans to come up with some new mechanism to automate this process, downtime is assumed.
* If you want no downtime, use one of the userspace replication solutions.
* Best option is to upgrade the master with pg_upgrade, then upgrade the slaves and re-copy your data.
* While it's tempting to think you could just run pg_upgrade on all hosts to avoid the copy step, that will not work as something in the system catalog changes which will break replication.
* No good options to speed up the slave copy - rsync will either use timestamps to figure out if a file changed (and streaming skews that), or checksumming (and checksumming is slow).

Is that still pretty much the situation today with 9.2 and 9.3?

Any good guides or BCPs for the standard procedure that emphasize limiting downtime and giving a good rollback path?

Thanks,

Charles