1) You cannot change the type of raid of a drive, ie to clone the main drive which is malfunctioning, you have to remove it, install the new one, resetup many things (first drive stores some info), then copy the stuff from the old drive to the new one. You can't simply turn on mirroring.
2) The unit cannot tolerate drives that spin down/up too slowly because it's timeout is constant instead of adaptive. This means your drives will spin up, down, up, down if they are older drives.
3) Icons on the user interface have inconsistent hot spots, so clicking on a word or icon doesn't always activate that function
4) The folder infrastructure makes it difficult to have more than one drive, and easily keep track of what's on it by drive. You need to mess with the directory structure using the GUI to make volumes which show up in the share list. DLINK's VOLUME_X structure is much easier to administer, and easier to move things around when one folder needs to be moved from one drive to another.
5) Client access requires typing in a password every time that system boots. DLINK DNS323 uses a password, but doesn't ask it every time - WinXP caches that ok.
6) No software updates yet. Still version 1.00
7) If the system has any problem with one drive, everything slows down to a crawl. Unacceptable for the recovery process, as well as normal operation.
8) You need to root the unit and navigate Linux via telnet to be able to fix problems like interrupted SMB file copies (a Netgear router I have cancels DHCP leases clobering everything in progress).
9) Simple GUI stuff like changing the admin screen timeout aren't available. A modern router has fancier GUI software. I could probably suggest 10 improvements here.
10) The server backup/restore options need a serious high-level explanation of how they work. Sounds nice on a checklist, and the (I) button on the front, which is supposed to start something (not a power switch for the NAS!) doesn't seem to do anything.
11) The unit complains when a drive is over 90% every time it wakes up or boots, and sends you an email about each drive if you have email notification turned on. Cannot configure the percentage or whether or not to notify on this.
12) Rooting the unit doesn't let you to keep a password on the root account. It resets after each boot. So you have to disable rootkit to allow external secure access.
13) The one most knowledgable person on the forums hasn't posted any new technical posts in 6 months. That's bad.