For anyone interested in really loading up the Microserver, I can report that you can fit a Lindy SAS/SATA backplane in the 5.25" bay, load it with 6 x 2.5" disks, fit another 4 x 3.5" disks into the main enclosure and connect both to a HP RAID adapter to give you better RAID options.
We've currently got this plus an iLO card, 4GB RAM and 4 x 2TB drives (RAID 5) plus 2 x OCZ Vertex 2E 60GB drives for OS (RAID 1) and another 4 2.5" bays free for future expansion. Runs Win 2008 R2 and acts as our small office AD controller, DHCP, DNS and file server. Does so much more quietly than a normal tower server.
Neat piece of kit this, might buy one for myself.