I've had a Matrix 6 for almost 10 years now, as well as a Matrix 1000 for about 15 years. I'll just post a few of my impressions here.
I can't compare its sounds to Classic Oberheims, since I've never owned any. It might not sound the same as a classic Obie, but it surely holds it's place against digital emulations of any sort. In a mix, it tends to sound dark and warm (might be the 30 year-old capacitors). In general, its sound is very suited to external manipulations such as delays, reverbs and the like. It simply flourishes when applied the right EQ, even if its a plugin. I love that. Compared to my other DCO synths (Junos, JX-10, Evolver) it sounds really nice, and a recurrent source of creamy analog pads, fx, eps, and basses. The Junos/JX , on the other hand, can reach stereo-wide chorus timbres, but never go as low as the Matrix 6. They complement each other nicely.
The cool features:
It relates very well with its sibling, the Matrix 1000. I am able to load patches to and from the Matrix 1000, without using the computer. By using the right features on both units, I am able to play a full 12-voice synth with a single patch doubled across both units, controlled by the Matrix 6. If I choose, i can also keep the 6 voices and make a 2-layer patch, with stereo widening achieve through detune. The results sound amazing. You need to have a Matrix 1000 for this, though.
Programming is very tedious. It has NOT got a data slider. All values need to be entered by pressing keys. Terrible. You might use an external editor, but still results are far from perfect. As said before, the Matrix processor is really slow. Every time you change a value on the editor, it takes a few seconds to update the Matrix. I even tried a BCF 2000 and a Novation Zero in sysex mode, the speed is still the same. In other words: forget those intense live manipulations. To counter that, it's got plenty of modulation slots (hence the Matrix name), but the envelopes are very slow, too. So, no snappiness here. The only option would be to assign a single parameter to be changed via the mod control on the left. Because of all this, it mostly becomes some sort of a "program-and-then-play" synth.
Now ,the issues:
The synth, due to its age, is fairly unreliable. I bought mine in excellent condition, and my studio is very well cared for. I've read somewhere that the components used on this synth are of an inferior quality compared to previous Oberheim. I can confirm that. The case construction is just about average, and the keys are light and fragile. Sensitivity is not great. Connections are very flimsy, I might replace and resolder them very soon for better quality connectors. Voice chips are also a problem. Every few months I have a quirky voice chip. I have to open the synth and apply either deoxit or isopropyl alcohol to try to fix them. This has been going on for the last 3 years, and I bet that very soon one of the chips is going to die. I have also changed the internal battery 2 times, and the last I had to solder a battery slot to make things easier.
During last year, though, my unit has started to develop some kind of alzheimer. Every time i turn it on after a while (1-2 weeks), the display lights up with @@@@@@@@ for all the characters. I have to turn it on/off a few times to finally boot the unit, and then recalibrate & factory reset. But then all my sound memory is lost, and I have to recall the patches using the tape load function. It is not the internal battery, as I changed it less than 2 years ago. Searching on old forums, I found the information that it might be the symptoms of a dying power supply. Very likely. This means that my Matrix is going to rehab soon.
I am obviously aware that these are like common maintenance routines for a 30 year old synth. But I compare with the Matrix 1000, which is about the same age, gets twice as much use, and has never failed on me. From all the vintages I have, the Matrix 6 is the one that needs the most care.
Since it sounds exactly the same as the Matrix 1000, and given that the Matrix 1000 is a more reliable unit (at least in my experience), I can only recommend a Matrix 1000 instead of the Matrix 6. The Matrix 1000 can also be programmed via software, and will save you some studio space. For the looks and the girls, though, the Matrix 6 is the one.