We use quite a lot of QNAPs at my work and I have a TS-412 at home. I generally find the devices pretty good - speed over iSCSI seems much better than SMB.
Just make sure you dont run out of space - I have had some major headaches because of this - why when they are setup they cant reserve a small part of the disk to avoid this is beyond me.
Also as you have noticed the support is pretty poor - they also have Skype support but when you ask something its at least a few hours between replies.
We are now testing some Drobo's as good support is important to us
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