Entry level graphic arts
Personally I don't think a WS motherboard for a consumer grade socket (and yes, I know i3s have traditionally got some more business spec features such as ecc ram support) really makes any sense. Especially seeing how cheap a low end x99 xeon is. I guess this is more for someone who wants a PC that runs for aages.
Asus is targeting graphic artists and engineers and students in these fields who can't afford a Xeon workstation at home (which really isn't necessary anymore). A lot of people play games, surf but run a quadro card and AutoCad or Adobe. especially if they need to render in 3-D. Those of us who are too poor to buy a $6-12,000 workstation opt for a gamer board with a hot processor. Some go with gamer GPUs in Cross-fire or SLI and others go the quadro route. The latter is more expensive but some need the special drivers to do what they do.
The stability issue between workstations and pc's is really a thing of the past and there really isn't a clear dividing line anymore. (There was a time when you had to buy a co-processor to do any serious math. There was a time when you had to go the server-workstation route if you wanted to do serious rendering or even use a workstation GPU. Now that the GPU has memory, not such a big deal.)
We're looking at this board because our GB X-58A-UD7 has been giving us some grief. Think I have the MB and system stable now and hoping can make it last a little longer. It's got a i7-980x but leans more toward a workstation with a Quadro K4000 card. We use it for the Adobe gamut, CAD, and run some huge Excel workbooks. As far as stability, personally we don't overclock much but are interested in most of the same topics o'clockers are interested in. For instance, advanced cooling since a processor can be left to run at 100% for hours.
As far as running for ages, it is pretty much a different assortment of the same features on other Z170 boards, same soldering and so on. So I don't think people go this route thinking it will last for all the ages. Besides, the technology is still changing too quickly to rationally think that. Our rig is 5-6 yrs old and we're stuck with PCIe rather than PCIe 3.0 for example. I think people consider it satisfactory as an entry-to mid-level workstation these days and may go this route for budget reasons for at home or studio work especially if the same has to do for games, tv, and other PC stuff. The # of cores and clock speed issue people are bringing up is misleading. We don't need dual power supplies as mentioned earlier because we are not serving clients. What we need is the Skylake architecture including a new chipset which surpasses comparable Xeons. Intel has made the new Skylake Xeons incompatible with consumer boards and server board manufactures haven't produced much in workstation boards for the new xeon processors, especially if you want to run a solid-state SSD in a slot. We hoping that will change and the old machine can hold out until they do. With Skylake, the lower power requirements for the same output reduces the cost and complication of cooling which has also occurred for workstation GPUs. Go green ya know, it's the holidays.