Parallels Server for Mac's management front end will be familiar to Parallels Desktop users. In the Server version, you can manage guest virtual machine instances on remote systems. A detachable console window is built into the management interface, replacing Parallels Desktop's viewer that required a user to be logged in. Parallels Server for Mac will launch one or more virtual machines at host startup and either suspend or shut them down when you shut down your Mac.
Parallels Management Console, which runs the same locally or remotely, presents a live view of the virtual guest's display. Unlike Remote Desktop or VNC, Parallels Server has the advantage of bringing up the console the instant the VM "powers up," so the BIOS and kernel loader text messages you'd see on a physical machine and monitor are sent over the wire. Parallels Server uses VNC for remote access to a VM, but according to Parallels, it isn't compatible with standard VNC implementations. If it were, the OS X guest problem would have an easier solution.
Parallels Server for Mac presents a mix of strengths and shortcomings that make it difficult for me to issue a simple thumbs-up or thumbs-down. I definitely like the direction that Parallels is taking, especially with regard to Parallels Explorer and Parallels Server for Mac's handling of VMs at boot and shutdown. Parallels also offers a free SDK for its Server product, providing IT with a chance to make up for some of what the core product lacks, or to at least automate tasks that typically call for menus and wizards.
But OS X Server as a guest of OS X Server is a nonstarter, and that was unquestionably the most anticipated feature of Parallels Server for Mac. I was able to get a guest OS X Leopard Server VM to work by using a work-around posted by users in Parallels forums -- a work-around of which a Parallels employee proved unaware -- but the machinations required to make it go left me with a lack of confidence in the product. Parallels needs to take another swing at this and, in the meantime, drop the price on its current effort to offset the product's unfinished pieces.