I am currently pursuing the M2M with its own SSID and a private password. This means that if the M2M is logged on to a Fritzbox I see 2 networks and can not log on one of the two. Theoretically, one could also assume the SSID and password from the home wireless router for M2M. One would then see only one network. Whether as well as transparent roaming is possible, I need to test yet.
As for the writing of the hard disk with data directly via USB 3.0 I am pleasantly surprised as Intenso a write speed of max. 75MB / s (1TB) indicates. When filling with MKVs under WIn8.1 were loose 116MB / s is achieved!
One star deduction there for the housing can not be opened without destruction and for the lack of user authorization. When you share data with friends, each full access and thus can also change or delete data. At least one guest access with read-only permission would have been nice.
There is a telnet access with which you can access the Linux system. However, the password is not known. Too bad, because there were a few other things possible in Customizing. FW updates it will probably be no more anyway.
So the bottom line is a small wireless Universal Repeater with integrated NAS based on Linux.