Firmware 6.0.8 just became available for the x86 based Netgear NASes. Interestingly enough, it is called “firmware” version, but to me (and others familiar with electronics and embedded systems) a firmware is low-level software running directly on the CPU/MCU. Maybe there are such components in the Netgear firmware too, but most part seems to be just updates to the NAS’ Linux environment (or more specifically: to the Debian Wheezy packages).
Turns out there was no need to worry. All three works flawlessly also after the “firmware” upgrade. Nice.