It is possible open the Hyper-V console for an individual VM without opening the full mmc.  You can do this either using the cmdlet that was just published by James O'Neill, or by creating a custom shortcut.

PowerShell method

See the recent post from James on his TechNet blog:
http://blogs.technet.com/jamesone/archive/2008/04/19/more-on-the-accessing-the-hyper-v-api-from-powershell.aspx

Shortcut method

Create a shortcut to:

C:\Program Files\Hyper-V\vmconnect.exe HostName VmName

If you have multiple VMs with the same name, you can also use the machine GUID:

C:\Program Files\Hyper-V\vmconnect.exe HostName -G VmGUID

Of course, in either case, you would substitute the name of the physical server for HostName and the name of the Virtual Machine, or the GUID, for VmName or VmGUID, respectively.

Thank you to James O'Neill and Cedric Davies for pointing this out to me!  This came up as a question during a presentation this week.