With the initial setup complete, the available services are pretty much ready to go. You can choose to have the server automatically configure new or existing workstations to access its resources and services, send invitation e-mails to existing users with computers that may already be configured, or set up access manually.
In its default configuration, the Mac Mini server includes two 500GB internal hard drives, with the second drive occupying the space normally reserved for a traditional Mini's optical drive. Like the MacBook Air, you can install software and even erase and reinstall the operating system by sharing an install CD/DVD from the drive of another Mac or Windows computer on the same network. You can also buy the $99 external USB DVD drive available for the MacBook Air to use with the Mini server.
There's no real right or wrong way to work with the configuration of the two internal hard drives. By default, they exist as two different, unpartitioned volumes (one of which is used as the server's start-up drive). You can keep this configuration and use both for storage or use one as a backup drive. You can also combine the two using RAID to act as either a single large volume, a striped volume for increased read/write performance, or a mirrored set in which data is written identically to both drives so that in the event of a failure of one drive, the server will continue functioning without interruption.
Each option is fine, depending on your needs or preferences. The one setup I wouldn't recommend is using the second internal drive for Time Machine backups. For convenience and a bit more security, I'd use a larger external drive that's at least 1TB.
The Mac Mini server comes with only a single Ethernet interface, but it also offers 802.11a/b/g/n wireless, making it an ideal choice in businesses and offices where cabling may be difficult or costly. If additional Ethernet interfaces are needed, you can use the USB-to-Ethernet adapter that Apple sells for the MacBook Air. The five available USB ports give you some room to expand Ethernet access.
Performance with the Mini server is good for a small business, but it's no barn-burner. With the 2.53-GHz Core 2 Duo chip and 4GB of 1066-MHz RAM, it can easily handle basic services for a few-dozen computers without buckling. Although you could theoretically support even more users, I'd suggest that you limit the number to no more than maybe four-dozen users. I'd also be hesitant about using it to host corporate Web sites for the Internet at large.
But for internal use by a small number of people, the Mini server does really well for its size and price.