[j-nsp] SRX upgrade procedure -ready for enterprise?

[Andy Litzinger]

We're evaluating SRX clusters as replacements for our aging ASAs FO pairs in various places in our network including the Datacenter Edge.  I  was reading the upgrade procedure KB: http://kb.juniper.net/InfoCenter/index?page=content&id=KB17947  and started to have some heart palpitations.  It seems a complicated procedure fraught with peril.  Anyone out there have any thoughts (positive/negative) on their experience on upgrading an SRX cluster with minimal downtime?

thanks!
-andy