I mainly use action rules to email tickets to non-techs in different parts of the business. Unfortunately instead of being able to email the complete ticket (as in when you CC someone on the ticket) you have to build the email field by field. It becomes much more complicated because we use a lot of custom fields. When you create a custom field it assigns a display order number to it and thats what you have to use in the email, not the field name you gave it. The problem starts when you alter the display order (people always want to move fields around on a form) because it affects all the others so then the email you created is no longer pulling the right fields because you changed the display order. Very shortsighted. The rule action needs a check box to just send the complete ticket. Would make my life so much easier.
Beyond that the rules are pretty flexible especially if you want it to change something on the ticket.