I have a D8B that I bought new in 2000 that has been virtually trouble-free. A few sticky fader motors, a couple of scratchy pots, and recently I've been suspecting the hard drive is on its last leg. But this is after ten years of nearly continuous use. Mine has been treated well, but two other used units that I installed in clients' studios ended up needed extensive service—including a mother board.
Like many of us here, I use my super-slick rack stuff when recording, and mix mostly ITB. So for a number of years my D8B has been relegated to being basically a glorified headphone mixer and router for using external effects units during big mixdowns that are otherwise ITB. It's really a great utility box like so many hardware controllers are. Coupled with a Z-sys digital patchbay, the board gives me great routing flexibility for my multiple computers and converters. The on-board converters and pres are obviously not "high-end," but are of sufficient quality to be used without concern.
If you're going to be working with lots of formats, some of which are antiquated, I think you'll find it a useful tool if you can get it up to speed. Make sure you have or get the Apogee clock card, without which the board can't be externally clocked. And I also highly recommend upgrading it to the 5.1 OS—though I think it's a total ripoff that Mackie has never dropped the price on it.
The place to go for service is S & X Pro Audio in Washington. (206) 575-1704