I've had my MDR since last fall. There is a LOT of information on the Mackie Hard Disk Recorders forum. I also strongly suggest you download the HDR (yes, HDR, not MDR) Technical Manual PDF from Mackie's site. If you ignore the sections dealing with the GUI, almost everything else pertains to the MDR as well. An essential add on (IMHO) is the remote 24, since it gives you 2 more locate points which are used for automatic punching, and makes switching between virtual tracks much easier. For the most part, I just treat mine like a 24 track tape machine. I've had zero problems with it.
Scott