ReadyNAS 6 discs and RAID 6?

I am seriously thinking of getting a Netgear ReadyNAS 700 with 6 of 4TB Western Digital discs for backup of a home network.

Any comments good or bad welcome.
The network has a mix of XP, Win 7, a few MACs and some smart phones.

Some specific questions come to mind.
1. If the shell is bought separate to the discs, how easy is it to 'build' the system, software wise? I am thinking about RAID 6.
2. Are WD discs a good choice?
3. Can the system auto shutdown from a UPS?
4. Is the operating system similar to Linux (I currently use Ubuntu on an old PC)?

Thanks (and seasons greetings)
BJ