We use standalone Zephyr in conjunction with JIRA, Confluence (both hosted OnDemand) and Stash.
What I can't work out is the justification for their pricing.
I pay Atlasssian about $10 per user per month.
Zephyr wants $80 per user per month, others mentioned are $25 per user per month.
Is test management really worth 5-10times as much as I pay for bug and content management ? Or 1000 times as much as I pay for source code and code review ? (Stash is $10 for a year for 10 users)
So we continue to use the Community Edition of Zephyr... I really like Atlasssian's pricing model and they will continue to be my vendor of choice until someone else can match their price/performance combination*
*For more than 10users prices can get high...