This is obviously a ecchi fanservice harem anime. That much is glaringly self-evident. I have no problem with that genre, honest, but this anime was not for me. I dropped it after seeing more than half of it, but I know the rest of the plot by reading spoilers.
I noticed that a reviewer named "Chasekun" compared Sekirei to Fate/stay night. All I have to say in response to that is...
"Are you nuts?! Have you actually SEEN Fate/stay night before, Chasekun?!"
The two couldn't be more different. While, yes, there is a very superficial similarity in the "Masters/Ashikabi with Servants/Sekirei" dynamic and that there is fighting between Servants/Sekirei. But that's it. Fate/stay night is far, far deeper and much more thought-provoking, especially the original visual novel— the anime adaptation is quite lackluster in comparison to the VN, but even the anime of Fate/stay night has much more substance to it than Sekirei. Interesting and well-developed characters and actual character development, dynamic plot (the VN actually has three different routes/stories each with multiple paths), actually well-thought-out mechanics for things like magic (this reviewer thinks so, anyways), etc.; I could go on but that isn't the point of this review.
Sekirei, on the other hand...
Story: Poor. There's not really much of a story here when you look past the feeble attempts at establishing a plot. It's pretty much exactly what is written (or rather, drawn) on the box. As I'm sure you've read in other reviews, it's basically an excuse to have 100+ super-powered chicks duke it out—oh, two or three of the Sekirei are bishounen instead. The story is written to basically allow for the premise of "big titty aliens with superpowers in a battle harem, inexplicably having fallen in love with a completely unremarkable spineless loser (lol, only in anime can this happen), beating the crap out of other big titty aliens with superpowers for an arbitrary reason". That may seem harsh, but it's literally what the story is when you sift through all the padding put in place to make it seem like there is actually something there.
Art: Mediocre. I'm kind of spoiled by series with far better artwork now, though, so I'm not impressed, can't help that. Also, I tend to like more realism in character designs, rather than the style of "impossibly wide hips, huge butts, and massive boobs". Also, there is something about their faces that just feels wrong to me... I think it's the eyes.
Sound: Fair. Nothing groundbreaking or amazing. Voices are decent, at least in the Japanese version (I'm not sure if there is a dubbed version of this yet, nor am I really inclined to find out). Essentially, nothing I didn't already expect, but that isn't a bad thing, exactly.
Character: Poor. Characters are pretty much static cliches meant to be the carriers of tropes commonly seen in harem anime. Let's see... the main male character is more of a pathetic weenie than Keitaro of Love Hina, and not even nearly as noticeable or amusing as him; he's just sort of... there. Main female character is... hmm, "empty headed" is the best way to describe her; she's one of those vapid "I don't have 'common sense' so I sound like a moron when I ask questions about things that should be self-evident to any normal person" types. After her we have a scary onee-san landlady (probably one of the most interesting characters in the story), psuedo-playboy but not really bishounen Sekirei, amiable tomboy lesbian sekirei (also one of the most interesting characters, and not because she's lesbian, mind you), lazy pervert bum guy and his twin tsundere lightning sekirei, token loli sekirei, lecherous old man type big titty hacker sekirei, possessive violent tsundere sekirei, sensual stripper older woman bottle fairy sekirei, bloodthirsty insane sword sekirei, main character's weird perverted somewhat domineering little sister and her shota dark-is-not-evil sekirei, his domineering smoker researcher mom, batshit crazy mega-corporation head, and many more largely irrelevant characters.
Enjoyment: Poor. Personally, I prefer stories that are actually substantial and not a flimsy cover for a ecchi fanservice harem situation. I like stories where the characters are actually modeled like real people with dynamic moods and personalities, and not essentially one-dimensional harem tropes designed for the sole purpose of ecchi comedy. I like stories that engage me intellectually and make me think, not mindless perversion barely hidden behind a cobbled-together plot.
Overall: Decent, actually. While I didn't finish it, I didn't exactly hate it. I didn't like it either. In the end, it does what it set out to do—provide ecchi comedy—pretty well. However, I'm not exactly interested in something lacking this much substance, since I'm a thinking type of guy. Basically? If you want to just sit back, veg, and watch something ecchi that doesn't require much thought and has lots of girls with big tits and butts? Sekirei is for you. If you want to watch something that actually requires you to pay attention to the story because it has an involved plot, with developed characters? Try something like Fate/stay night (especially the original visual novel, it's a fantastic read) instead.
