There are two ways I look at Gabriel DropOut. One is as a CGDCT anime and the other is as a comedy. While the two usually go very well together I separate the two of them for a reason. As a CGDCT anime Gabriel DropOut is alright. Vinge and Satania are cute, and at least Gabriel has a cute design, even if her personality is annoying. However, as a comedy anime it is painful.
The biggest issue I have with Gabriel DropOut is that it's not funny. Many of the jokes all boil down to the same thing: "The angels act like demons and the demons act like angels." That's actually an interesting idea but the problem is it's not very funny. And it's certainly not funny enough to fill up 12 episodes. However, still the show likes to repeat this joke over and over and over and over again. That and Satania bullying (having funny mean things happen to Satania) is the bread and butter that this show has. Both of which got boring pretty quickly. They do sometimes mix in other jokes but even those jokes fall flat most of the time because it's predictable how they end up. Some of them are jokes I've seen from other shows in the past. The execution of these shows as well tends to be lackluster. There isn't enough variation in the setup or the punchline of the joke so it only adds to that samey feeling. Comedy is subjective but I have a hard time understanding what's so funny about this show. Rather it's attempts at humor usually annoy me more than anything.
The characters range from good to incredibly grating. As it turns out the demons fall into the former camp while the angels fall into the latter camp. Satania is dumb but can be pleasant to watch due to her attitude and the life she brings to the show. Vigne is basically a normal girl as a demon so like a normal girl, she's cute as well. I wouldn't consider either of the characters very well developed as the show never really pulls them apart from their normal behaviour or gets them into situations where they have to grow. There was a moment with Vigne where she showed some more depth but for the most part, the show lacks in that department. That said the two demons are fine characters and at least are likeable. The issue with these two is that it depends on who they're paired up with for how enjoyable each segment is. They're usually paired with the angels which sadly doesn't help them out.
Gabriel is a whole mess of issues. First off she's basically an okatu character played straight. She's never more interesting than that, and her cynicism and her lack of caring get really annoying to watch. It's even more so annoying when they make up this backstory of her being a perfect little angel before getting tainted by the modern world and video games. That actually could have been an interesting story if Gabriel cared about retaining her angelic nature and if it happened slowly through time. Instead, it takes one night, throwing out all illusion of having character development or depth in exchange for a cheap laugh that isn't even funny. What's worse than her bland and uninteresting personality is that there's nothing that makes her likeable. She usually ends up acting pretty mean to her friends, which only serves to make her character less likeable. Thusly. I have no reason to want to see her on the screen nor care about her well-being. It even hurts her cuteness because she has a great design yet it's hard to really adorable or enjoy the looks of someone who I don't like. The ruins part of the magic that could be there.
Raphael is a sadist, and if she had any redeemable traits that'd be ok. But she doesn't. Rather she's pretty much a sadist and nothing else. Her target of prey is poor Satania. Sometimes this works well and is funny but most of the time it doesn't. Satania bullying only really works when Satania is being played due to her own faults. Otherwise, it's cruel and seems unfair for poor Satania. What did she do to deserve being bullied? She has her flaws but not enough to justify the amount of bullying she receives in the show. I personally have a problem with characters getting mistreated whether by the world or by other characters and since it ends up happening so often it only adds to the annoyance that this show can provide. But going back to Raphael, that is the main point of interest with her, and probably the only notable one. And like Gabriel, she gives no reason to like her, and thusly she's annoying to have to watch, as well as again being a bland character.
Unlikeable characters are fine when there is a purpose behind them. Say if they are villains, or if they're used well for comedy. However, the comedy gotten from these characters are stale and not worth while. Furthermore, they clash against the notion of caring about the girls which hurts the CGDCT aspect of the show. The show doesn't work that well all together, and the root of the cause is its failed comedy. Thusly, I imagine how one feels about Gabriel DropOut depends on how funny one finds it. If one finds it funny then it's some of these problems feel like less of an issue. But personally I didn't, and thusly I relied on the characters to win me over. While Vinge and Satania worked, the angels did not, at least for me.
Despite Gabriel DropOut's poor attempts at humor there were a couple of episodes that did shine. These episodes proved that the show can throw in some good material when it wants to. There is a later character that appears named Tapris who is proof of this. However, the show spends more time mulling around the same jokes to really go anywhere and that's it's loss.
The art and animation were solid throughout but never seemed notable enough to give it praise. The music was ok, although I don't really care for the OP very much.
Overall the show is inconsistent and has issues with its humor and its characters, however, it is pretty cute and does have some merits. This is a show that you can probably tell whether you'll like it or not from the first couple of episodes. They never really move on from that type of material. Personally, I don't recommend it but there are worse shows to watch.
An unimportant note: The CR subs for this show were absolute trash. They kept on inserting random jokes instead of translating the actual line. Although that's CR's fault not Gabriel DropOut's fault.