Pros Low power consumption
Two 7200 RPM drives can be configured as RAID 0 or 1
Great price considering Snow Leopard Server is $500
Cons External drives have performance limited by FW800
Not optimal design for server -- why IR, wireless, two video ports?
Summary Nice upgrade to original (white plastic) design. Many people buy these as high-end Mini desktop computers. As a server, the design is a bit lacking but the price is excellent -- an Apple bargain!
However, Mac OS X Lion, due Summer 2011, will have server features incorporated, thus eliminating the high price server edition, making this less of a bargain unless Apple drops the price. The expected Thunderbolt connector will make performance of external drives superior. Probably best to wait on this if you can.