I recently received the second and third shirts I've had made by Proper Cloth. A few thoughts:
First, the website is generally excellent. Easy to use, good images of the fabrics, etc.
Second, I used measurements from a shirt that already fits well and they seem to have been followed pretty accurately. I made a few small changes with the second order (mainly to address minor issues with the shirt I had based my measurements on) and now have a good fit. The shoulder slope options are a big help, I haven't used the posture options but they're nice to have available. Very easy to understand how to take and record the measurements thanks to the website (videos, general design, etc.).
Third, please offer more fabrics. Especially more name brand fabrics. And heavier oxfords. And linens.
Fourth, please offer the option of unfused collars/cuffs/plackets for all collars (even for an extra charge). Right now some collars get unfused, some get fused. This isn't obvious until you start going through all the collar descriptions. At least make all the button-down collars unfused. I ordered the standard button down collar without realizing that some of the other BDs were unfused, and now I'm realizing how important wrinkles and puckering are to a nice OCBD
Overall, considering the cost I've been very impressed.