Several months ago, Shana Rusonis @Atlassian has published this great post and an infographic about the popularity of Jira, and shared some of the usage stats (PDF) from Jira's largest customers.

Here are some of the findings:

• Jira has sustained over 100,000 end users for one of Jira customers;
• It can support over 5,000,000 issues in a single instance, while the average number of issues for large customers is 1,400,000;
• On average, 400 workflows (and 900 custom fields) are used by Jira's largest customers.

Jira Misc Workflow Extensions, one of the top 5 (out of 1600+) marketplace apps for Jira can help you create workflows to support any number of use cases. Most can be configured without code, and when needed, additional workflows can be customized to support nearly any requirement with simple Groovy scripting.
This one app can take your workflows beyond limits to enhance your team's productivity. You can try it for free for Jira Server and Jira Data Center (as well as Jira Cloud).