Domains are brilliant things, but should only be used for real network customisation, such as policys, active directory etc, just as Technogab has commented on.
I use a workgroup for my home wireless network, where i can connect to my music of any laptop, or my psp, and also connect to the internet.
I am currently in the stages of setting up a domain network for my the company i work for. This will be run under server 2003, where as the workgroup is just done under xp.
Adam
I use a domain. It is far easier to manage policies and control the network. Plus my DNS server runs off the AD server too, so I can manage that as well, rather than relying on my ISP's. I like being able to log my printer server into the domain and manage the printers that way. So much easier.