Based on their explanation, usually the M.2 device connects with the onboard chipset then to the CPU, but the Ultra M.2 connects directly to the CPU. In theory this sounds pretty cool, no more bottlenecks for expansion cards. Wonder if there are reviews out there that can solidify this.
I get about 980MB/s on M.2 myself. Where are you seeing 4GB/s speeds reported? Or do you mean this is theoretical?
Also the samsung sm951 will be 1600/1000 Mb/s read/wrie and 130K/100K IOPS 4K random reads/writes.
http://www.custompcreview.com/news/2014-samsung-ssd-summit-samsung-sm951-m2-pcie-ssd/21564/