Good for cheap, simple prototyping.
For simple, single or double sided, low technology, boards they are good. Generally, they get the orders correct and ship quickly by DHL but on one occasion I have had them send two batches of one board and none of the other design. This week, I've spent 3 days trying to get files uploaded and approved so I will look elsewhere now as timing is important to me. PCBWay are probably at their best for prototyping ideas that you've had in your head and want to try but are not urgent. The strategy I use for prototyping is to send them maybe 5 or 6 designs and combine postage, this gets the costs of the boards down to an incredibly low level. Hobbyists would find their services excellent. For professional or volume production use I would be inclined to look somewhere else.