In his writing, I haven't seen a team book where he's been able to let every character shine yet. There's one star, and a lot of hangers-on. This worked well in Iron Man, where the book is clearly about Tony Stark, but it really made his Uncanny X-Men run go off the rails, when it became all about neo-conservative Cyclops and the rest of the mutant wallpaper.
Previously fleshed out characters like Emma Frost were relegated to getting humped by Cyclops, while being used as a telepathic walkie-talkie and missions and literally being told to shut up when trying to give input. Storm would go whole long stretches without a line. All that did was frustrate the holy hell out of any fan who was reading for any character not named Scott Summers. "The Sisterhood" was honestly the biggest clusterf*** (for lack of a better term) in terms of a plot that made sense that you'll ever try to find.
Now, I gave his run on Thor a chance, after having read most of the JMS run, and barely made it through the first arc. Hell, from his first issue alone, Thor has Lady Sif in his bed, but isn't in the mood because after the events of "Siege", he "misses his brother, Loki". The same Loki, who but a few months before had STOLEN Sif's body. And she just sits there and takes it.
That's probably another detriment... his female characters often only exist to pine over, or sexually service whoever the protagonist is to make them look good. Even when Maria Hill is given panel time to look tough in his Iron Man, she ends up in bed with Tony.
"Fear Itself" was the "everyone gets a magic hammer" event, that ended where all the heroes get a magic something else handed to them by Thor, because Tony Stark got Odin's attention (even though Thor was gonna get murdered) by sacrificing his sobriety (say whut?)
Finish that up with his interviews... all through that Uncanny X-Men run, there were tons of X-Positions and other interviews that had fans dying to know what happened next. And the hype over everything fell flat through the whole first year. By the time "Utopia" rolled around, fans already had begun wondering how Emma Frost's bargain with Norman Osborn to be on the Dark X-Men would affect the story. So Fraction, in an interview, stated that it wasn't a feint, for real, Emma was back to being a villain, and had her reasons.
Two weeks later, she jumped ship back to the X-Men, screwing over Norman Osborn, and Matt Fraction literally said, "Well, I had to lie in the interview because everyone was guessing Emma was gonna betray Norman for Scott. I had to throw them off. Sorry, guys."
At that point, I never took an interview he had to promote a title seriously, and now, I avoid his titles like the plague. There isn't enough of a moral center for me, it's just male control freaks trying to dominate their corner of the Marvel Universe and sleeping with whatever alpha female they can while dismissing any emotional concern for them. Gets real old, real fast.