I find this interesting. I like to hear what customers (I prefer clients) have to say. I haven't been in this game very long, but this is what I can tell you of my own experience so far. I am an independent shop tech.
Some mechanics are stubborn - they won't listen to new ideas or even client suggestions. That doesn't do anyone any good.
Some mechanics think they're always right, and anyone else is an idiot that disagrees with them. This again benefits no one.
Why do most people seem to have negative experiences with their dealership? It's just how they run. I don't doubt that there are great dealer service centers and techs out there. The issue is that they tend to have a high turnover rate of new techs. Essentially, there's a lot of inexperience floating around.
The local BMW dealership has a lot of work. They have 100 bays, 40 techs and 20 service writers. Just by principle, it's so much easier to just "guess" at a repair, let the service writer deal with the crap when you're wrong and then make another guess and hope it works. Shotgun diagnostics. Benefits no one, except for maybe the tech because they're getting paid for more work at the client's expense and dealership's reputation. No bueno.
In an independent shop you don't have that wall to hide behind. That is a good thing. As a tech, you're no longer "tech #27" you're "Mike." That anonymity is gone. Repairs and diagnosis need to be correct the first time. There are instances where you'll be thrown off course. It happens. In these instances, it makes a world of difference when you have data on WHY a repair direction was made and sold to the client. SHARE this information with them. They will usually be understanding as you're being honest. Sometimes people are just unreasonable - do your best and take it as a learning experience. They may still come back next time.
Issue #2 with dealerships: service writers. Again, I realize not everyone is this way. Generally, dealerships prefer their service advisers to come from a NON-TECHNICAL background. They have no idea what the tech is talking about. Their goal is to be best friends with every client - earn their trust. An ex-tech service writer is the best kind in my opinion. He will have the knowledge to look at a repair order and agree or question a tech's decision. If it seems way off, he calls BS and kicks it back to the tech to get better answers.
On the subject of wait times. Man, I've been on both ends of the stick. I took a single wheel and tire to pepboys one weekend (we don't do tires at my shop. Odd one for me because I've always had access to a tire machine). The lady at the counter said it would take about 10 minutes to have them put "together." Now I know it only takes about 30 seconds on a tire machine, but whatever. Two hours later it was done. Yes I waited. Should have left but kept getting reassured it was about to be done. Waste of my time. I was still nice to the tech. Knew it was a waste for him as well... said "thanks man, I appreciate it" and didn't get even the slightest of recognition in response. ****.you. I also had one client that authorized 10 hours of work one day that was due at the end of the day. He had nothing better to do but waited for 8 hours in the lobby. I felt bad. No one wants to do that. I missed lunch to get him out of there sooner.
My final concern - unreasonable clients. Oh yes, I've seen a few. You don't know what's going on in their life and what other problems they may be having. It's best to just approach every situation with everyone's best interests in mind. Sometimes you're just going to lose. I did a set of drum brakes on a clients car awhile back. Then the parking cable seized up and warped the drums. Replaced everything and sent it off after testing. It showed up again a few days later for making a rubbing noise. Tested/rechecked/sent off. It kept coming back. I lost a lot of time and money to try and make things "right." Well the fact is that there was nothing wrong with the brakes. I noticed the guy just rides his brakes forever when coming to a stop. Brought it to the attention of the service writer/owner who would constantly get a barrage of emails and texts from the client, asking for loaner cars and eventually claiming all of us techs were incompetent. The owner looked at the car with the client and (surprise!) Still found nothing wrong. He just got another email stating the brakes are still making noise. The response was "There is nothing wrong with your brakes." Yup.
I know people question labor times quite a bit. The fact is that we don't know how long it's REALLY going to take. Sometimes a supposed 3 hour job takes a whole day. Sometimes it takes an hour. You pay for expertise. The first time doing something always tends to take longer. Techs are always in a constant battle of winning or losing on repair orders. Set labor times are the only way to make it fair. Also, as far as doing your own work. Great! I'm all for that. I understand that sometimes it turns into a daunting task you weren't expecting. You have to understand though, that when you bring something like this to a repair shop we have to look at it and may have to charge a diagnostic fee. If it's pretty obvious of a task... yeah probably not. But if it's one of those "my car does this sometimes and a mechanic friend said it's "this" but didn't look at it" issues, let us help you help us get it right the first time. Also understand that when you give us a half-completed job, it is still on the tech if it doesn't work right. We HAVE to tear it down all the way to know it's done right. Sometimes it is, but oftentimes it isn't. And then nobody wins.