I have one - the Stratofighter. It's very much like an Extreme Ratio MPC with some blade and handle modifications. The blade metal is N690; good stuff. The handles are 6160 aircraft grade aluminum. The back-lock system is one of the most robust I've ever seen.
It's a tough, overbuilt survival/combat folder, a decent cutter (flat grind), and runs about 50% less than its (alleged) ER MPC counterpart. I have found it a bit more tricky to sharpen than some other blades, but it holds a very sharp edge a long time. I would assume this is also true of the smaller "covert" folders and their larger fixed-blade combat knives, like the Interceptor. I did a review of the Stratofighter a while back on this forum. Bottom line: there's no criticism of the knife, itself, that is not also probably due the ER MPC, which quite a few seemed to admire.
The marketing copy seems over the top to many, but it accomplishes its goal - getting your attention (ER also markets somewhat like this, as well). I've seen some on forums try to scare potential buyers away by citing the potential legal implications of buying something labeled a combat or fighting knife. That's absolute rubbish. Others, who have never even picked one of these up, let alone used one, will tell you it can't possibly be a good cutter - but it has proven to hold an edge and cut as well as my $400 Mission MPF-1 with an A2 tool steel blade. Of course, neither of those cut as well as my Fallknivens or my CSC Bowie; so be it. Would I buy another DO? I don't really need more tactical folders, and I don't need a large combat knife. But, if they came out with something else useful to me, yes, I'd consider another.
A great deal of criticism has been aimed more at the company's outspoken owner, rather than the knives themselves, and at the perceived issues between him and ER. But, there always seem to be issues like this, out there, affecting one company or another. I try to stay focused on the knives.
The photo is of the DO Stratofighter next to my Mission MPF-1 A2 for size comparison. I also tested the DO cutting ability against this Mission.