The following are some noteworthy points regarding Process Builder:

1. A Process's API name must be less than, or equal to, 77 characters, and it's always associated with a single object.
2. Using Process Builder, you can't delete records. If you want to do that, you have to use Flow with Process Builder.
3. To set Text data field to blank, you can use {!$GlobalConstant.EmptyString}.
4. The Process owner will receive an e-mail from Salesforce. If the Process failed at runtime or if any fault occurs, the error or warning messages might refer to a Flow instead of a Process.
5. The process follows all the governor limits that apply to Apex.
6. You can have a maximum of 50 active rules and processes on any object. Rules include Workflow Rules, Escalation Rules, Assignment Rules, and Auto-assignment Rules.
7. Process actions are executed in the same order in which they appear in the Process Builder.
8. You can't delete an active process; first, you have to deactivate it. Once you have deactivated a Process, you can immediately delete it.
9. If a custom field is referenced in a Process/Flow, you can't delete that field.
10. Before you change a custom field’s type or name, make sure that it isn’t referenced in a process that would be invalidated by the change.
11. An immediate action on a record update obeys validation rules.
12. A scheduled action on a record update skips validation rules.
13. If any of the actions fail, the entire transaction fails and an error message is displayed.
14. File type custom fields aren’t supported in Process Builder.
15. External objects and deprecated custom objects aren’t supported in the Process Builder.
16. If a single action group includes multiple Update Records actions that apply different values to the same field, then the last action’s value is used.
17. The total number of process criteria nodes that are evaluated and actions that are executed at runtime is 2,000.