The one dark shadow over the X8 is the MU-MIMO "capable" line in the product spec. Here's the disclaimer:
MU-MIMO feature requires firmware upgrade. MU-MIMO firmware upgrade not currently available for this product, but currently anticipated to be released before the end of 2015. MU-MIMO capability requires both router and client device to support MU-MIMO. Please see www.netgear.com/mumimo for more details.
(Don't bother hitting that link above. It just takes you back to the X8 product page.)
Will Broadcom / NETGEAR ship MU-MIMO before the end of the year? Or will this turn into a repeat of the Quantenna MU-MIMO debacle?
Which brings us to NETGEAR's unannounced MU-MIMO introduction: the R7500v2 Nighthawk X4. The v2 confirms rumors heard earlier this year that some router makers were removing Quantenna from their 4x4 designs and putting in the only working MU-MIMO solution to date: Qualcomm Atheros'.