As noted, they are light, have low recoil, don't chop much, make a cool sound, are easy to maintain, and cost a lot.
They have long term issues with the membrane pad that contains the eye toggle and on-off.
They are not always very efficient, though a friend of mine gets a good 9 pods + hopper on a 45k/68 ci tank.
I disagree with the "nothing special" statement, I really like the feel of a Dm4. That is down to preference, of course.
The earlier released Dm4s apparently had lots of issues. These seem to be cleared up in the more recently manufactured guns.
There is some issue about the lack of a diode on the board which would prevent voltage spikes to the solenoid. The main deleterious result of this flaw is that the batteries run down faster than they would otherwise. If you are handy, you could easily solder in this diode yourself.
Evolve is apparently working on an aftermarket bolt kit. If it is anything like the kit they made for the older style Matrix, it will be worth the money for the efficiency improvement.
Honest Injun, that's what I know/ think.