I have a DDM2, i got it on a strong reccomendations from a few people. used it for 2 years no probs, then the clutch went for some reason so got it repaired and whilst it was being fixed i borrowed a mates makita 8406 to do a couple of holes on a job.
both me and the apprentice did one hole each through 300m cavity walls built with 4" concrete block (using the same marcrist gold core bit i always used) and both of us were pleasently suprised with it. apprentice asked me why i didn't have one as it was half the size and weight and seemed to do the same job? I'm not sure!
DDM2 is back and has done another 20 holes since with no problems, but if it breaks again the repair and servicing cost coupled with the weight of it might be a factor in "downgrading" to a makita 8406
although i would defo reccomend marcrist gold cores with whatever machine you drive it with