Linksys has announced that it's the first to ship a working MU-MIMO (multiple-user, multiple input, multiple output) router, the $280 Linksys Max-Stream AC2600 (aka the EA8500). That grumbling you're hearing is coming from early adopters who already bought MU-MIMO-"ready" routers and are still waiting for the firmware needed to turn that feature on.
MU-MIMO is the first step toward the coming generation of "Wave 2" 802.11ac routers. The real deal will also be capable of bonding several channels on the 5GHz frequency band to create one super-wide 160MHz channel. On its own, MU-MIMO promises to improve Wi-Fi performance in homes with multiple users streaming music and video over the network at the same time.
Why this matters: The best that the most recent Wi-Fi routers can offer today is SU-MIMO (Single-user MIMO), which is capable of servicing only one client at a time, forcing everyone else to wait their turn. That can causes glitches in media streams if the client hasn't buffered enough data to paper over the gaps when the router needs to momentarily stop the stream to service another client.
MU-MIMO routers can service multiple clients simultaneously, eliminating the round-robin situation. The hitch, however, is that the client devices must also support MU-MIMO, and those are few and far between (but they're not unicorns).
The Linksys EA8500 is based on Qualcomm's MU EFX MU-MIMO technology (the first round of MU-MIMO routers were based on Quantenna chipsets). Qualcomm's chipset can support four spatial streams to deliver throughput up to 1.733Gbps on the 5GHz frequency band, and up to 800Mbps on the 2.4GHz band (Linksys adds the two numbers together and rounds up to arrive at the "AC2600" designation). The EA8500 is also equipped with a 1.4GHz dual-core CPU and sports one USB 3.0 port, one USB 2.0/eSATA combo port, and a four-port gigabit switch. Its four external antennas are removable and upgradeable.
Linksys tells me the EA8500 is available now at the Linksys store as well as a number of online retailers, including Amazon, Best Buy, and Newegg. I expect to receive an eval unit early next week and will put it through its paces as soon as I can.
Note that Linksys does not consider the EA8500 to be its top-of-the-line consumer router. That distinction belongs to the Linksys EA9200, which is outfitted with three Wi-Fi radios (two on the 5GHz band and one of the 2.4GHz band). If you don't anticipate acquiring client devices with MU-MIMO capabilities in the near future, a tri-band router might be a better bet.