In general, I liked the CN-570. The configuration menu structure was clear and easy to use and the box was very quiet in operation. The BitTorrent, UPnP AV and FTP features were a plus and the fact that it could be either a NAS device or a external USB device was a feature I've only ever seen in one other NAS on the market. And I've never seen a NAS device that could use either an IDE or a SATA drive. Not bad for a box with a street price of $85!
But of course, there are downsides including bugs and poor performance. As a result, you wouldn't want to use this device for heavy-duty network use. And the documentation was worthless in many respects. Consider section 9, creatively entitled "Performance of the Question":
Q No sleep mode function? A No sleep mode function
Got that? Reading between the lines I'd guess that it's impossible to put the drive to sleep when not in use, but that's only my guess. And there were many other sections of the documentation that were equally as bad. Finally, for software, there was nothing included to do backups, which is one of the main uses of these types of devices. And if your setup machine has a slot-loading CD drive, you'll need to forego using the setup utility, which is Windows only anyway.
If you're willing to overlook its slow network speeds, bugs and generally worthless documentation, the CN-570 would be a handy device to have around for its Swiss Army knife-like collection of features.