I heard about DGM awhile ago, but I never managed to start the series until recently. I read the first vol to the latest chapters within a few days, and I have to admit there is potential.
Plot: Young orphan joins secret organization to defeat "akuma" and he meets a variety of different characters and learns about his past.
Starting out it feels episodic, with Allen going out for each mission and for many of the action fights it's confusing with the sudden changes in POV or when he "levels up". Halfway from into the series, we finally get to the main idea about antagonists and some background history about the Black Order. There are short chapters devoted to some of the supporting characters and their individual histories.
Characters: Large cast of main and supporting characters. I admit I started to become slightly confused since people appear and disappear from parts of the chapters frequently. I feel that it's somewhat too busy, and some of the characters don't really have much time devoted to their individual stories. Still I find Allen relatively likable as a MC and no one was extremely annoying in any of chapters.
Art: Yes, I did notice a big change from the beginning chapters to the latest chapter released. I'm in favor of the new art changes, the line work is cleaner and I find it easier to follow the panels. There is a strong "gothic" look to DGM with strong use of contrasting colors. Unfortunately, some of the fight scenes are confusing and tend to take over multiple chapters.
Recommended: Yes. It starts out kind of loosely plotted, but later on it shows potential for a interesting story.
Edit: It restarted approx back in '15 but so far I'm still totally lost. Since it's a quarterly release I hope they plan to resolve some of the major mysteries SOON. I'm debating if I want to re-read the series since so much time has passed b/t chapters. I wish they had a summary before each new volume.
e: it's been 7 yrs and I have no idea how and what the plot line ended up. I feel like the story will continue in my 30s in a confusing way.