Yes, I have a pair and they are my main speakers. Here are a couple of thoughts about placement.
Firstly, remember that the drive unit line-up is upside down compared with the conventional: the bass unit goes on top. The transmission line vent is at the bottom.
According to the manual, they are designed to be used closer to rear walls than typical speakers of their type and size. In my experience this doesn't necessarily mean they like to be close to the rear wall. Their already powerful bass can be quite overpowering in these conditions.
I've also got the B&W dedicated stands. They look nice and 70s, but I prefer my own stands made of square-section tubing. The boxes may be placed vertical or horizontal. (I've never tried horizontal.) There's an alternative floor-mount method using a sloped miniature stand that angles the sound up towards the listening position.
Because the drive units are located off-centre, if the boxes are more than a couple of metres apart, B&W suggests placing them with the drive units lined up closest to each other (that is, on the inside edge facing you). If you are using them close together, have the boxes with the drive units on the outside edges facing you.
The foam front lining on my pair has perished, by the way; little granules of the original material still keep drifting out whenever the speakers are moved. This doesn't seem to have any bearing on the sound, though.
I first heard them about 30 years ago and couldn't get over their ability to convey power and delicacy. Upstream of them was a Thorens 160/Quad 33/Quad 303 system. About 10 years ago I was lucky enough to get the entire system from the original owner.
The DM2as are big, heavy and frankly don't fit in with the average household. However, people who have heard music at my home are remarkably consistent about one thing: they really like what they've been listening to. Of course, the DM2as can't claim all the credit, but clearly they are something special. They're not for everyone - I've already mentioned the bass and I wouldn't call DM2as the last word in dynamics either - but as I mentioned they have other virtues.
Current system includes Linn Sondek/Quad 34/Quad 405-2. The DM2as have also sounded great with Quad IIs. Although I would prefer to use my Alan Hobkirk pre-amp, it doesn't have a moving coil input. The Quad 34 does have a MC input, but the soundstage seems constricted by comparison.