Since you want feedback on shops, I'll give you my experience with one vendor in particular.
I personally would avoid Ballistic Fab because they are a very poor shop in my opinion, based on my interaction with them on a diff cover. Poor attention to detail, and surprisingly poor design skills despite a plethora of high tech R&D equipment. I would have forgiven a lot of this had they been at least a little graceful about the situation, but they came off as indignant and inconvenienced by dealing with me, the customer, so I wrote them off. Too bad for them though, they lost all future business from a guy who owns 3 off road vehicles.
I ordered a diff cover from them in a group buy when they developed one for the M226, and the first one didn't fit, no big deal, it's in development right? Well I send them detailed design info on where they failed to provide adequate clearance, I do mechanical design work for a living, so I think I gave them some pretty useful info on what area to not put metal in. We are talking less than .010", which in the world of synthetic oil might as well be the grand canyon, but still should be very easy to design in enough room so it would seat flush on the mating surface, which is most definitely a requirement if you ever want to keep oil in the diff.
Additionally they had pretty poor welds for such a high end shop, they had very obvious porosity, which means they didn't set it up right, left it dirty, or all the above. I let my co-workers, including 2 mechanical engineers and a toolmaker have a look at it. They were not impressed. Most telling, I had my Dad look it over, he is a weld quality tech and a certified welder, he said that it would have failed if he was inspecting it. It would have held oil, and strong enough to hold up to abuse, so I didn't have a huge issue with it, but it just wasn't as polished as it should have been, coming from an established, supposedly high end fab shop of that nature.
Well, they tell me they will have adequate clearance that on the next one they send, okay, I didn't ask them to make that commitment, but they did. They sent me another one that wouldn't seat on the flange, same clearance issues. It was better but still not right. Sure, I could have hit it with a grinder and made it work, but I take any warranty on the rest of it into my own hands if I do that, and with less than stellar welds still fresh in my mind, I'm not so sure I want that, so I call them back and ask what we can work out. At that point they just wanted to give me a refund. Okay, after that was agreed upon they get really hard to get in touch with. Thankfully I'm very persistent, friendly, but persistent. They drag their heels sending me the return label, finally milk that out of them, then I have to call daily to get my refund after 2 weeks of waiting for them to do it on their own after they got back both the covers they sent me. On top that they keep initial shipping, which I guess is their right, but shows they really didn't want to make a good impression. I send them a polite message asking about that, it was ignored.