Yeah, we've been in the process of planning the update in light of the security fix. We're likely just making the jump to 9.2 in the process so that'll be handled soon.
I think you should update your PG version and then resync your standbys (ie, apply a fresh base backup) at the next convenient maintenance window.
We did apply a fresh base backup last night to ensure our current standbys are in a good state. I was mostly wondering if there were some better way to continually monitor the state of our standbys on an ongoing basis aside from checking pg_last_xlog_receive_location, etc. I realize it's no small task but thought maybe there was something I had missed.
In the end, I think this just helps nudge our upgrade along :)
