Fanfic An Enjoyable Read
For someone who hasn't read a metric ton of fanfiction(I read it, but not as much as others so I didn't recognize as many cliches when I first read this), I quite enjoyed Clell's story. It's witty, well versed in both canons, and has logical plot progression(though this is mostly a character piece). I know that many people complain about the power disparities between the Marvel Universe and the Potter Verse, but that's just the way it is. From my comic book reading experience, both the Marvel and DC universes outclass the Wizarding World in power and efficiency by many, many orders of magnitude. It's not an exaggeration to say that most street level(read: muggle/non powered) humans from the Big Two comic book universes could solo squadrons of Death Eaters on their own, let alone imagining what papa Iron Man and his Merry Marvel Marching Band entitled The Avengers could do.
As for the question of why the Potter Verse masquerade would even exist in a world where magic, aliens, mutants, demons, gods and science fiction tech are already accepted by the public, let me remind of something. Doctor Strange is thought by most people to merely be some new age kook. Spider-Man can never, ever get a break from the Daily Bugle. Thor and Hercules are regarded as just exceptionally powerful mutants living under the delusion that they are divine. Other mutants are feared and hated, even by people that would have no reason to(such as their own family members). Heck, Galactus isn't even publicly known. It isn't a stretch at all for me to believe that Harry Potter style wizards were persecuted in the past within this particular AU and took on their own separate society.
Harry initially comes off initially as a Mary Sue, but as the story goes along, the author shows some of his flaws and ambiguities, especially during the flashback scenes before he goes to Hogwarts and his weird refusal to even consider who his birth parents were. As mentioned elsewhere, Dumbledore is the villain of this story, but in the end he is more manipulative than truly evil, with everyone's best interests at heart in his mind. Also, not all of the wizards are completely opposed to muggle culture(Sirius even becomes a superhero in this story!). Anyways, great fun. If it's a Mary Sue fic, it's a rare GOOD example.
Fanfic Too Much Sue
It's a fun read at first- What would Harry do if he loves technology as much as magic, having grown up with Tony Stark? The problem is that the author clearly loves the Marvel universe and is determined to show how much better it is than the Harry Potter universe. Harry seems to solve all his problems by asking for help from his Marvel Superhero friends. He gains plenty of superpowers from a hidden exoskeleton to personal training from Captain America, Marvel Universe-type magic, etc.
But superpowered Harry isn't the only problem. He's not even interested in the magical world per se, he just wants to be there to make it better. He vehemently refuses to learn about his biological parents, as if that would be an insult to his adoptive father. He makes friends with just about everyone, acting almost prophet-like in his forgiveness and willingness to work together. There's no conflict at all that isn't solved by the end of the chapter...
Fanfic Fantastic Idea, Poor Execution
They Wasted A Perfectly Good Plot. The summery sounds brilliant, but in this particular instance it comes across as a fix-it fic for the entire wizarding world using liberal splashings of the Marvel Universe to either jazz it up or show it up. The result is a bit as if someone had decided to chrome plate a fourteenth-century castle, or the family china. And not done it particularly well.
The writing style leans hard on the telling, light on the showing. Dialogue tends to be simple and exposition heavy, and the narrative is, at its worst, explanatory paragraphs. And there's much more dialogue than narrative.
The universes are clumsily melded with an obvious bias toward Marvel. Marvel Universe rules take precedence to Wizarding World rules without exception, up to and including the way magic works inside the walls of Hogwarts. Apparently Wizards have been Doing It Wrong for centuries, and wandless magic is easy as walking. The Wizarding World doesn't fry Harry's tech because Tony Stark Built It, and it becomes the answer to too many problems. As for Marvel, apparently Chaos Magic is now being handed out to ten-year-olds like sweeties, and the Avengers can and do all band together to co-raise Tony Stark's charity case kid.
In terms of characterization, Harry seems to have caught some sort of contractual genius bug from Tony. The first chapter establishes that at nine years old, Harry broke through Tony's security system in a half hour, a feat that took Reed Richards six hours. The second chapter establishes that he's better at Transfiguration than Professor McGonagall. All that, and he still manages to break down house boundaries and charm all the girls. It might help that his peers are all pretty well spoken themselves.
In short, while Harry isn't a Sue of the highest degree, he is definitely a Sue. The writing style is clunky, cumbersome, and dry. The characters are flat, and both worlds deform to fit either Harry or the author's needs. What they don't do is reform to fit one another. This fic could have been beautiful, had the author had more respect for source material and been more skilled at characterization, world building, and descriptive writing. It had the potential to be brilliant. It's not.