Most of the custom PC companies are good.
They (custom PC builders) are just as good or just as bad as any other custom builder. Once in a while, some unfortunate customer WILL get a bad system. Normally, the builder will try to fix the problem if the time factor is not too much. If not, they will just walk away from the customer. This is a fact of life!
Do some comparison shopping, read customer reviews (some of these reviews are fake), and then take your chances. The majority of the shoppers will do ok, and will get a good system.