We have a Dell Power Vault 745N in service at our organization which is running Windows Storage Server 2003. For the most part administration is rather simple. Plug it in and let it run! NAS devices are designed for file sharing which does not require a lot of constant tweaking as does a production SQL, Exchange or application servers might. If you keep your NAS stripped down (which is best for performance)patching is pretty simple as well. In fact you may want to speak to Dell support on this. Dell has recommended with past NAS devices not to patch the OS unless you have a specific need to do so.
Printer sharing is not a featured selling point for NAS devices, but never the less the server will do a good job at this role.
As for the difference between standard, workgroup and enterprise editions, these apply to the size environment your in. Enterprise edition is designed for a large organization and will accomodate an increased number of processors and higher memory capacity than does standard or workgroup editions. If you have a domain and are a small to medium sized organization, the standard edition is the way to go. Workgroup is best suited for small businesses operating in a non-domain environment where security is less a concern.
This answer is rather general but hope it helps!