hey,
i've been considering this lately myself. I have read a couple of reviews (macobserver and sventech [or something like that]) but there's not much else out there on this device.
I emailed their tech for some answers and this is what i know so far. (forgive my ignorance on some of these things, i'm not super familiar with raid or how these devices work so my comments may seem like no-brainers)
1. RAID 5 - if you have a 4x500gb setup and want to upgrade it to 4x1tb you gotta back up the 4x500gb array, add all 4 drives and create a new array and then copy your data over. I think this is quite common but i was hoping to just add 1tb drive at a time, let it rebuild and so on. Not a big deal but something to consider since you'll need to have a back up drive(s) big enough to copy your data to.
2. You can't just use it as an enclosure. if you set the raid switch to 0 ("not in use", described in manual) then it sounds like it defaults to span. So it seems there's no way to just add 4 drives without some sort of raid setting
3. this may sound silly but one of the options on the raid switch is for mirroring or striping with 2 drives so i thought maybe you could use that setting, add 2 more drives and they would just appear as normal drives not associated with the raid. as i'm sure you guessed, the other 2 drives would not appear. naive...maybe, but thought i would ask them anyhow.
anyhow, that's all i know...i'm still on the fence with it as of right now but still leaning towards it...i know i can't have everything but this seems to be pretty close given the price range (qnap 419 seems to have it all but is 2x the price)
hope this helps and hope someone else could chime in with their experience with it.