Fiberglass boards are not that raw. FR4 material is base for many printed boards used in audio , computer industry.
I have friend in Croatia , who have small company for makeing PCBs , and best printed boards that he can make are on PTFE(teflon) base and conductive paths are made from pure silver or cooper.
That material is best for audio and is used for UHF circuits too , besouse of exeptional electric caracteristics.
I'd agree about the E-bay thing. The boards I have bought off there are very good quality and I have had no problems with them on any circuits I have built. Plus the price vs. quantity can't be beat. I always believed that circuit stability and reliability was more dependant on the layout than the actual board material. And unless your working in the microwave frequencies I woulden't worry about the capacitance between layers or traces. Hope that helps you some.