A little disappointing for us X79 owners who were actually looking forward to IVB-E, but at the same time I don't see myself hopping on the X99 bandwagon. The first generation of new RAM is generally pretty slow for its own generation. When DDR3 just came out, there was only a slight jump in speed over high-end DDR2(DDR2 was at 1200+, DDR3 launched at 1066 and 1333).
I'll take my quad channel, high speed DDR3 over that quad channel, same speed or only slightly faster DDR4 that requires a new board and CPU.
Besides, 32GB of DDR3-2800+ and a six-core IVB-E should be powerful enough for a few more years and by then X119 or whatever they plan on calling the next HEDT platform should be out and I'll be ready to upgrade again. Hell, X58 is just now starting to lag behind a little, and it's been around for what, nearly 6 years?
I suppose my point is this: I can justify an upgrade to IVB-E and some new RAM in six months, but I can't justify building an all-new system just for DDR4 and a slight CPU performance boost in a year and a half. To those that don't already have an HEDT platform, this may be appealing, but DDR4 needs time to mature on the open market before I'll consider going there...
EDIT: Another point is that with any of the SB, SB-E, IVB, and Haswell i7 chips, you put a slight OC on them and you'd be hard-pressed to find a real-world application(not benches or crunching/folding) that actually stresses all cores, much less stresses all cores to 100%. Why waste time with four more threads that run a little slower when eight/twelve threads aren't being fully utilized? E-peen, that's all I can figure...
Looking back, I should have built an X58 rig when they were new. I would just now be looking to upgrade, lol. That being said, with this X79 rig I don't even need to upgrade to IVB-E and it should last a few more years. I'm really just looking forward to IVB-E for higher RAM speeds and a new overclocking adventure. I'm sure a lot of people will love their X99 rigs, but the appeal to me is really just getting a look forward.