For the most part they just work but with limitations to the file size. Many have FAT32 volumes which gives you that 4GB file limit.
Maybe I've owned one of the ones you are considering.
Today I have the Dlink DSM-G600 and a V-Gear Landisk.
I'm having a hard time finding reviews for network external hard drives (meaning I can plug in the external hard drive into my router using an Ethernet cable to share it over my network) on Cnet.com I can narrow down the reviews to External Hard Drives, but then I don't see anything else to narrow it down to network enabled drives. Am I missing something or what? I did a quick general search on this site and I got back results for humongo data center looking HDs. Any help would be appreciated.
P.S. If you know of any other review sites, please let me know, in addition to purchasing sites (other than amazon.com and newegg.com)