I have been going to Top Shelf for almost 30 years.  I grew up eating their shredded beef burritos at the Scottsdale and Shea location which has since closed.  I don't live in Mesa, but any time I have a chance and am in the neighborhood, I stop by the Southern and Dobson location.  The shredded beef has not changed and is probably some of the best shredded beef you will find in AZ.  Their margaritas are tasty and their chips and salsa are amazing.  This is a great place for a tasty Mexican food dinner.