I have been using the same DT store since 1997, but have been using them before that too. Only twice in the past 25 years have I been to another tire shop. Once was to Pep Boys for some cheap tires for a truck I knew I was getting rid of (after rebates and sale prices it was like $125 for 4 tires mounted and balanced). The second one was I had bought some used tires and brought them to a local fly by night tire shop to get them mounted (actually traded the rims the tires were on for the mount and balance).
Only a few minor problems with them in all that time. Once I was pulling out and the center cap came off and rolled into traffic and was run over. An employee saw it and went and got it, by the time I got back inside the store, the manager was already on the phone getting me a new one ordered for me at no cost.
Bought a set of tires for my Elantra (Goodyear Comfortread, counter guy talked me in to them) and within 10 mies I hated them. Went back and they took them off and upgraded me to some TripleTreads at no cost.
When I had the tires on my truck installed last year (store matched DTD $100 off ad. Cost was supposed to be $740 total with tax, tires, mounting, balancing and certs, but walked out paying $600 out the door), I wanted one of the "good" old tires put onto the spare rim. They took the good tire and rim and stuck that as the spare and put a new tire on the spare tire rim (I have 5 matching rims, but the spare rim has a huge gouge in it). I saw it as I was about to leave. Told the manager and he went out and switched them himself.
In his hurry, he grabbed a chrome valve stem instead of a black one. I did not notice it till a few days later. Not a huge deal, but when I went back to get the tires rotated and a bolt removed/patched last week, they took care of it for me.
My mom goes there exclusively also. I have called the store and told them what she needed and they take care of her. They did mess up one time and did not pro-rate her tires with certs when she got new ones (I think it was under my phone number, not hers, she did not know). One call and they credited her with the difference.
By waiting for their sales and using their credit card, I have been able to get some really good tire deals.