Have used the Hippotizer HD media servers, and the Doremi Labs V1HD deck for playback in live televiseed before Andy.
What do you need to know Andy ?
The Doremi works great with serial machine control, it does well with switchers and show control. The Hippo HD works best with DMX protocol (thus control via the lighting desk), and is in general WAY more flexible and powerful than the Doremi. We've seen a big swing to Media Server playback over deck based (hard drive or magnetic) in the last two years.
Let me know what your questions are...
MODE Studios http://www.modestudios.com
Contributing Editor, Entertainment Design Magazine
Art of the Edit Forum Leader
Live & Stage Event Forum Leader
HD Forum Leader