I skied them last year for some time. If you check the "Gear Review" section, there should be an M1 review there.
They're super stiff boards and probably one of the top 5 stiffest stock non-racing skis you can buy.  To handle them well, you'll need to be a strong skier, otherwise you will get tossed around.
The M1 has no speed limit and if you wanted to straightline a 2,000-foot shot, you can do that.  I measured the effective edge at 164cm and according to Moment, they weight 9.9 lbs.  As you would expect, these skis excel in non-powder conditions.  I've found the 192cm version to be a bit difficult to whip around in tight spots, but that's not what the M1 is made for.  They're great in the crud.
As for powder, these are NOT powder skis.  On a couple days, I unexpectedly skied the M1 when it was 8-16" of fresh.  It took a lot of energy to keep them afloat.  Granted, the rockered version (the Garbones) would be much better suited for soft-snow conditions.
As for durability, I have no issues to report.  The top sheets do show some chipping, but that's only cosmetic.  Bases have been bomber so far.
If you think a Dynastar 194cm Legend Pro or a Rossi 194cm Squad is worth $650, then the price of the M1 is certainly justified.
Hope this helps.