I received the Tetra a couple of days ago. I did have to first connect through the Ethernet-over-USB port to initialize the device. I could not establish an Ethernet connection on the RJ45 port until I did that, even though my local DHCP server provided the Tetra with an IP address. After initialization, I was able to use the WebGUI over the RJ45 without issue.
I was sorry to see that there are no wall-mounting plastic bosses on the case like those on the MKV. I had to rig up something to mount the device in the vertical plane. I had to lie about my time zone to get the right time displayed in the system logs, even after changing the default time servers and having my local DHCP server provide a NTP server parameter.
The wifi reception is good, maybe better than that of the MKV, but still not good enough for my placement. Transmission is very good. I found that external wifi cards with Atheros AR9271 (Alfa NHA, TP-Link WN722N) and Realtek RTL8187 (Alfa NH) chipsets work quite well, even when both are attached simultaneously (through a powered hub, of course). However, the Realtek RTL8188 chipset (used in the Alfa NHR) causes unpredictable instabilities such as WebGUI lock-ups and out-and-out kernel crashes, requiring power cycling.
I plan to get an external wifi antenna amplifier to improve the 2.4 GHz reception of at least one of the external adapters. (They don't do 5 GHz). If need be, I'll buy a high gain sector antenna to couple to the amp for even more reception boost. Lots to do!