Your best bet would be to go with a known reputable brand like other people have suggested, unless you have a particular need to go with some other product (as I had).
I was looking for an ethernet network drive solution, as more than one computer will be accessing the drive (thinking it would be more convenient than moving it around with a USB/FireWire cable, plus it would be a great place to store everyones movie and pic libraries as well as backups)
I tried contacting ximeta.com
about their product, because it looks pretty cool. It took them 5 days to get back to me, which seems like a long time for a simple question. I went with a competitor.
I have a Freecom 500GB ethernet & USB capable network drive. I only just got it yesterday, but seems to work fine. Supports remote FTP access and can handle multiple users.
Looking at the support forums on their website, some complaints have been about access speed. I wasnt really concerned because I am using it mostly for backups and images (movies were only a secondary incentive, bit it seems to run .mov files without too much trouble). Although their help forum seems to be single handedly managed by one tech person, their telephone support was more than adequate (at least, the UK branch was).
The Freecom should be shutdown when not in use, as it tends to get pretty warm when in use for a while. That's not a problem for me though, as I only plan to use it intermittently.
Feel free to check them out at freecom.com