I find the quality to be great, but it depends what you would compare them to. Resin casts will usually have some imperfections.
I took a few shots of some
FW 30k resin marines prior to cleaning if it is helpful. This is from the Loken vs Abbadon set;
Here is a few finished
FW pieces;
Hope this helps, I would definitely recommend buying some to check it out first hand. There's a lot you can do to fix some of the minor imperfections, and the models themselves are usually pretty awesome.