I've built three systems with ECS boards and never had any problems. One was the K7S5A and can't remember the model number on the others but they were based on the Via KT133A chipset. They may be plain Jane boards with little or few OC'g features but the designs are usually good and perform very well for a stock board.
I used to do a lot of OC'g with the early celerons when you could coax a 50% boost through the FSB. Economically it made a lot of sense then. However, with as cheap as Athlons are anymore, coupled with only incremental increases in real performance, I don't think it is worth the trouble now. Under those circumstances, all you really want is a good clean stable board and that seems to be the niche that ECS occupies.
Regarding crap mobo's, my worst experiences are with MSI. I've build numerous systems using Abit, Asus, Epox, MSI and ECS. I have had more failures with MSI than any other. In fact, when I think about it, the only mobos that have completely failed me were all MSI's, three of them.