I thought that I would chime in and give my thoughts...
I have been running unRAID for about 3 years 4.7, and recently upgraded to 5.0 and then 5.05. I run a 7 disk system on a Supermicro C2SEE system with a AOC-SASLP-MV8, Celeron 430 / 2Gb.
I chose this hardware for the best support, least problem, low power. This is exactly what I wanted out of a file server.
More recently I have built a Xeon 1230 / Supermicro / 16Gb hypervisor box (Win2012R2-HyperV). I run a full time Win8.1 VM which I use to record TV, Sickbeard, Couchpotato, SAB and a bunch of other tools.
I am most confident with Windows, but like the idea of having a rock-solid file server for my "Production" XBMC clients. It is not the fact that it is Linux based, it is the fact that it is an appliance that does ONE job very very well.
The only time unRAID gets rebooted, is when I need to swap a disk.
Moving forward, I have had great service out of the hardware and the fact that it will not support x64 based unRAID 6.0 is not a big deal. In real world terms this hardware is old and has already returned it's value to me.
I don't run plugins on unRAID. The main reason is because I do not want to sarifice any of the following:
1) My time in keeping up with the quirks
2) Stability of unRAID
3) Upgrade path for unRAID
I have read countless threads during the v5 development where uncompatible plugins were the cause of issue.
unRAID 6.0 with an included hypervisor would suit me well. I could run a full time Windows "utility" machine, and consolidate my hardware to just 1 box. This is important to my powerbill, my time. and the stability of my home network.
Plugins have been underutilised by me because they do not inspire confidence.
Keeping other apps isolated off to an additional VM moves them away from being in the realm of support for Tom, allowing him to focus on what is the core product. This is a good idea.
Look forward to seeing where the development goes!