My experience so far with component clubs has mainly come from ordering from Gigagolf, where I've gotten irons, hybrids, wedges, and fairway woods and I've been absolutlely amazed at the quality for the price. Also have an Acer driver and 3 wood made by Hireko which are OK, bought cheap as preowned clubs.
I especially wonder when I see people complaining of quality problems with some of the brand name stuff, whether quality from some of these smaller manufacturers isn't sometimes better. The cheapest brand name stuff is still much more expensive, and yet they seem to be cutting corners in some cases on the quality of some of the components. To me, you know when you order from a component builder that you can get the exact fit you want, and your choice of quality shafts and grips. So it really comes down to the quality of the heads.
And of course there is some low quality component stuff out there as well. Some stuff with too cheap shafts and grips, etc, made to look like brand name stuff but not perform like it. You have to do a little research and read reviews, find out what other people are happy with. But there do seem to be a number of custom component builders out there with lots of satisfied customers.