Workflow rules are a great tool for automating processes in Salesforce, but there are some limitations to be aware of. First, workflow rules can only be triggered by certain events, such as when a record is created or edited. This means that if you need to trigger a workflow rule based on something else happening in Salesforce, you'll need to use another tool, such as Process Builder. Second, workflow rules can only operate on certain fields. So if you need to update a field that's not included in the list of available fields for workflow rules, you'll again need to use another tool. Finally, keep in mind that workflow rules can slow down your Salesforce org if they're not well-designed - so make sure to test your workflows thoroughly before deploying them!