pg_upgrade + streaming replication ?

I've got a 3 node cluster (1 master/2 slaves) running 9.0.x with
streaming replication. I'm in the planning stages of upgrading to
9.1.x, and am looking into the most efficient way to do the upgrade
with the goal of minimizing downtime & risk. After googling, the only
discussion that I've found of using pg_upgrade with a streaming
replication setup seems to be this (nearly) year old thread:
http://web.archiveorange.com/archive/v/9FNVlDWGQtpyWVL54jlK

In summary, there is no way to use both pg_upgrade and streaming
replication simultaneously. I'd have to either use pg_upgrade and
then effectively rebuild/redeploy the slaves, or not use pg_upgrade,
and reimport all of the data. Is that still the latest status, or are
there other options?

thanks