They're actually pretty mediocre cases unless you're watercooling or heavily into customization.
Despite their 'giant' size, it's not a very efficient 'giant', and it's almost impossible to fully utilize the space. Ease and neatness of routing cables is a distant second to what you can get in well-designed tower/mid-height cases. Despite all the fans, case airflow relies on brute-force rather than efficiency, because there's too many wrong directions for the air to travel. The fan HDD mounting and cooling is effective but crude, and offers zero vibration isolation. The case material is entirely 1.0 mm aluminum (even on the corners and edges) and feels rather flimsy compared to what you can get from companies like Antec, CM, Li, or Silverstone, especially for the price. Fit/finish of panels is good, but the screws can strip the aluminum threads a little easier than they should, and the add-on pieces like the mobo tray and horizontal mobo support could use slight tweaking for optimum fit. There are no front jacks/ports available, requiring you to go buy your own, and the case is deep enough that cables routed to the back panels often don't have much slack to work with. Casters are supplied, but regular pads are not, and the available MM acrylic feet
are badly designed. And oh yeah, don't forget the cost - most definitely a niche market.
But who cares about all that, right? They're BIG!!!
...and this concludes MpG's in-depth review of MM cases.