(I was ASE certified *many* years ago so I like to think I know BS from a shop when I smell it).
I stumbled onto Marshall's after 8 years with a well known Phoenix-area shop. I'll leave the name out of it, but suffice to say the shop got rid of the two gentlemen running the front office and things went down hill quickly. My first experience with Marshall's was after my '94 Saturn overheated while driving down the freeway. The "other guys" told me it was a faulty fuel pump and a radiator hose had burst as well. The bill would be nearly $1000 due to the fuel pump being inside the fuel tank, and they'd have to drop the tank, etc, etc.
I wasn't buying it, and service had been going downhill as I mentioned above, so I called around and decided I'd try Marshall's. After a day of lengthy troubleshooting, Marshall's determined that in reality the fuel pump was just fine, but that 2 of the 3 temperature sensors had failed, causing the car to run as if it was "cold" all the time. Thus fuel mixture was rich, acceleration stalled, etc, and finally the engine overheated because of the faulty sensors.
All told I left the shop with about a $300 bill and the car has run fine for the last year. In addition, they are *always* up front about what things *need* to be done, and what things I should think about, or just keep an eye on. I feel like they're always trying to save me money and do only the necessary work. I have talked a lot with both Joe and Pat, and they are always straight up with me.
They follow up on every service with a courtesy call to see if I'm still happy, and spend as much time with me as I need describing the options and discussing the plan for repair.
Everyone will have a less than stellar experience with just about any shop at some point, but I've not had one yet with Marshall's. As long as they continue to provide this level of service, they've got my business and I'd recommend them to anyone.
Why not a 5-star rating? Well, there just isn't anyone/shop that's perfect :)