I talked quite a bit with custom aquariums and they were a top contender for me while ordering the tank. I think their build quality looked great. It came down to two factors for me. I wasn't sure I wanted a framed tank since I hadn't decided at the time if I was going to put a canopy on top of the tank to cover the upper frame. This was a relatively minor consideration because I've had framed tanks in the past and it hasn't bothered me much.
The more important factor for me was their lack of options for overflow styles. I wasn't a fan of their overflow system. They also have an option for a Stealth box overflow but because of the flow I wanted circulating between the display and the sump I would have needed to add two stealth boxes. This pushed up their cost a bit compared to competitors for an overflow that ultimately wasn't really what I wanted.
I also worked with Waterbox. I loved the look of their tanks and got great reviews for build quality, fit and finish. I started moving forward and even paid the drawing fee with them and ended up canceling. The process was annoying because their reps weren't responsive and with every modification they would continue to jack up the cost. They were already the highest quote I was considering and after what seemed like minor changes it increased the price over 30%.
In the end, I went with Glass Cages. They are widely sold as the "middle ground" tank but they were responsive, easy to work with, reasonably priced and still able to make a custom overflow and euro bracing for me. They are at the very least worth getting a quote from. I'll update the thread on how the tank looks once I get it.