I have to say I disagree with most people in this thread about the criticism of AMD breaking backwards compatibility. While everyone would love to have hardware with endless upgradability, having this only would become useful after ~4-5 years when there is a significant upgrade, but then everything embedded on the motherboard would be outdated. If we were to have real compatibility across several generations we would need to make motherboards more simple, modular and barebone like back in the 286/386/486 days, where motherboards were basically more or less just expansion ports. This is an idea that I like, at least in theory.
We have to remember that this platform is meant for workstations, which makes reliability the most important trait. Motherboard makers are already barely maintaining support for any motherboard beyond 2 years, and they certainly don't test each model with enough hardware before shipping a BIOS update. As we've seen with AM4, the compatibility with older hardware is questionable at best. And while AMD motherboards are getting the same premium prices as some "premium" Intel boards, certain makers still fail to deliver the same quality (*ahem* MSI, Gigabyte…). If anything AMD should focus their energy on two things; 1) Firmware testing ahead of product launch 2) Put pressure on motherboard makers to do their best when making the BIOSes. A few hiccups after a product launch is excusable, repeated problems three months later is a deal breaker for workstation use.