If you use any NAS (or a SAN) devices, what do you use? And I'm referring more to larger scale network storage than your home PC or home theater system.

We've had very good experiences with our NetGear ReadyNAS devices but I'm in the market for something new. The NetGear's aren't the cheapest ones around but they do what it says on the box. My only real gripe with them is the lack of decent scalability.

TheCus devices seems to be rather powerful as well, and you can stack upto 5 units together. But that's where the line stops.

I'm now looking for something that could scale beyond 100TB on one device (not necessarily one unit though) and find it frustrating that most NAS's come in 1U or 2U at most.

Maybe I'm just not shopping around enough, or maybe I prefer to well known brands, I don't know.

So, what do you use?
How well does it work for you?
And, how reliable / fast / scalable is it?