Speed: The print was ready after 2 days. The transport agency took additional 3 days, so I received the parts within 5 workdays after the order.
Communication: I did not use the service of Treatstock before. So, I was surprised to get a photo of the pieces after the print. This is a helpful feature. I did not have contact to the manufacture company.
Quality: I think the design of the part is one of the major premises for quality. One type of a part was printed mostly correct. Some edges were a little bit roundish. I could correct it with a rash. A second part was not printed as expected. A 1 mm hole in a cylindric body appears only at one end. I guess the printing process is not suitable to produce this part as I have designed it. This might be caused by my limited knowledge of how to design a part for 3D print.
Nevertheless, the whole process was smooth and easy to use. The result will not prevent me from using it again.
Printing started the same day that I ordered, just a few hours later. Received the whole set of ordered prints three days later, carefully packaged. Good quality prints, little to no need for additional sanding etc.