I own one. A Mark II (I believe), 24 channels, 8 busses.
I like it, though its the only console I've used so I have no basis for comparison in terms of sound quality. I need to clean some of the pots, which I'll get around to eventually.
Some things I like:
Sounds pretty good.
Routing is fairly comprehensive. I can monitor off the main L+R mix, cue mix, or tape returns with the push of a button. Another push of a button assigns Auxes 1 and/or 2 to the cue mix output, so you don't have to mult off the Aux sends.
Talkback input is on an XLR and not a built-in mic, so it allows you to use a mic of your choosing. Talkback can go to the cue mix, slate to the buss and main outputs, or both. The cue and slate buttons are next to one another so you can go to both with one push.
Operates at +4, so it was quite easy to interface with my HD24.
Mono switch, which some similar consoles might lack.
Insert points on all channels, busses, and main L+R outs.
It's pretty easy to figure out. I learned the ins and outs of mine with no manual or anything.
Some things I don't like so much:
Only three Aux sends. Two are switchable pre/post, the other is fixed post.
No Aux returns. You have to bring them back on spare channels, tape returns, or the two Echo Returns (the Echo Returns are pannable and assignable to any buss, though).
No direct outputs. I think models later than mine did have them, though, so this isn't necessarily applicable to all of them.
Buss outputs are unbalanced, but on XLRs and pin 3 hot. Not a big deal, really. You just have to make a custom harness to hook it up to your recorder. I made one with Mogami cable and Neutrik connectors (XLR on one end, TRS on the other), for about $75.
It's not an inline desk, so you have to adjust your trim pots when you switch the channels from the mic inputs for tracking to the line inputs for monitoring and mixing. What I do is track my drums to the first 8-10 channels of my HD24, then set those channels on my board to the line inputs and adjust my trim pots, and I use higher numbered channels for my overdubs. So this shouldn't be a problem if you aren't using a lot of channels simultaneously for overdubs, or if you use outboard pres. It does have eight tape inputs for monitoring...there is a switch that changes between monitoring what's on a buss's output or on it's tape input.
I think that this board was intended when it came out to be used with 8-track tape machines, hence the eight busses and tape returns. It's pretty easily adapted to my HD24 (especially with the HD24's input normalling...saves me from repatching). If you're pretty minimalist in the outboard stuff you use (1 or 2 delays and reverbs, that sort of thing), it should serve you pretty well. I wouldn't spend an arm and a leg on one, obviously, but if you can get a good price on one that isn't shot, go for it.
Oh yeah, another thing that I forgot about. The System 8 had an optional sidecar you could get which added eight more channels of preamps. To connect this sidecar, there are a number of tie line inputs on the board for plugging into the busses and aux sends. So, if you so desired you could patch outboard pres into the busses if you wanted to buss a channel of outboard pre together with a channel or channels from the board. Just last night I was thinking about how difficult it would be to construct a matrix that would allow me to use outboard pres as if they were board pres...basically you would plug the pre's output into the matrix and that would then allow you to route it to any of the busses and also to the aux sends for cue mixes or sidechaining or whatever. Just a thought.