Much like D-Link's new interface, QoS or "Media Prioritization" is handled by a drag-and-drop mechanism, but caters for devices, applications and games, with more granular details able to be entered by the user if needed. Parental controls are somewhat limited, offering Internet access scheduling and blacklist capability.
The Smart Wi-Fi mobile app doesn't give access to all the settings, but contains enough to be useful. You can view devices on the network, alter guest and Wi-Fi settings, change parental controls (minus the scheduling), adjust QoS, and interestingly fiddle with port forwarding.
We tested with firmware 1.0.00.003, and used iPerf to determine the maximum wireless speed at three locations: the next room, immediately upstairs with some furniture in the way, and one room away from immediately upstairs.
The wireless client used was an Asus G550 laptop with a 2x2 Intel AC7260 wireless card, as an indicator of average performance. Each WLAN is set to WPA2 personal encryption and a clear channel is chosen. Where possible the highest channel bandwidth is chosen, either 40MHz or 80MHz depending on the wireless standard. Where appropriate, transmission standard is set to 802.11n or 802.11AC only.
Due to the variable nature of wireless and surrounding WLANs, each unit was tested multiple times at various times of day to achieve a best case scenario performance value. Your own environment will see different results.
The XAC1900 lags a bit in 2.4GHz, although it's nothing critical. Still, we'd have hoped for a little more competitiveness.
The XAC1900 provides the slowest 802.1n 5GHz scores for the first two locations, by a noticeable margin.
802.11ac performance generally hits the mark across the board.
Storage was tested over gigabit LAN with a SanDisk Extreme NTFS formatted 64GB USB 3.0 drive plugged into the fastest USB slot, transferring a 100MB file via SMB.
Linksys has a strong showing in USB performance, only bested by the Asus DSL-AC68U.
I can't help but feel disappointed with the XAC1900. The split out, giant power-modem brick, the slow wireless performance for the price, the laggy UI and the comparatively limited feature set compared to the Asus and AVM alternatives. While it's possible most of this could be addressed in a future firmware update, for this price we'd go with another option.