An AMD Ryzen is unlikely to be my next desktop's CPU
I'm probably going to wind up building a new home machine this year, to replace my current five year old one. One of the reasons I haven't been doing much on this yet is that both Intel and AMD only recently released their latest desktop CPU lines, Kaby Lake and Ryzen respectively. AMD has not been particularly competitive in CPUs for years now, so there's been a lot of hope attached to Ryzen; plenty of people really want AMD to come through this time around so Intel would face some real competition for once.
I have an unusual reason to be interested in Ryzen, which is that I would like ECC memory if possible. For a while, one of the quiet attractions of AMD is that they've been much more generous about supporting ECC in their CPUs and chipsets than Intel, who carefully locks ECC away from their good desktops. If Ryzen was reasonably competitive in CPU performance, had reasonable thermal performance, and supported ECC, it would suddenly might be worth overlooking things like single-threaded performance (despite what I've written about that being a priority, because I'm fickle).
The best current information I've absorbed is via Dan McDonald's Twitter, here (original, with more questions and so on) and a qualification here; unfortunately this is then followed up by more confusion. The short form version appears to be that ECC support is theoretically in the Ryzen CPUs and the AM4 chipset, but it is not qualified by AMD at the moment and it may not be enabled and supported by any particular actual AM4 Ryzen motherboard, and there are some indications that ECC may not actually be supported in this generation after all.
The really short form version: I shouldn't hold my breath for actual, buyable AMD Ryzen based desktop motherboards that support ECC RAM (in ECC mode). They may come out and they may even work reliably when they do, but ECC is clearly not a feature that either AMD or the motherboard vendors consider a priority.
With ECC off the table as a motivation, the rest of Ryzen doesn't look particularly compelling. Although AMD has gotten closer this time around, Ryzen doesn't have the raw CPU performance of Intel's best CPUs and perhaps not their good thermal performance either; for raw single CPU performance at reasonable cost and TDP, Intel's i7-7700K is still close to being the champion. Ryzen attempts to make up the deficit by throwing more cores at it, which I'm not excited by, and by being comparatively cheaper, which doesn't motivate me much when I seem to buy roughly one desktop every five years.
(As an additional drawback, current Ryzen CPUs don't have integrated graphics. I hate the idea of venturing into the graphics card swamps just to drive a 4K monitor.)
Still, Ryzen's a pretty good try this time around. If I ran a lot of virtual machines on my (office) desktop machine, Ryzen might be an interesting alternative to look at there, and I hope that there are a bunch of people working on cramming them into inexpensive servers (especially if they can get those servers to support ECC).