Server-based networks have the following Pros and Cons:
PROS:
+ Central Management
+ Shared login for easier access and greater accountability
+ More secure (easier to patch and push updates in enterprise)
+ Easily accessible network resources (shares, printers)
+ Potentially cheaper (if you spend $200 on thinclients instead of $800 on fat clients)
+ More features (VPNs, Remote Services, etc)
CONS:
+ More expensive (especially for smaller networks)
+ Single point of failure (Unless it has back-ups and redundancies... then see above)
+ Complicated to manage (requires skills and knowledge above and beyond regular desktop users)
+ Expensive licenses (you get gouged on licenses and software just because it's a server OS)