Why do some like this movie?

What I generally noticed about this kind of movies is that you either love it or hate it. I've watched a lot of them and this is the feeling I got while reading people's opinions here in IMDB.
As for me, I liked it. It's something different, new and fresh. Actually I like many of those "real footage" movies, with the exception of "Paranormal Activity 2" and "Paranormal Entity", because they give me the feeling as if I'm watching something real; "Quarantine" for example felt as if I'm really watching a live coverage of a zombie-like virus epidemic and this really appealed to me. I might also add, and that is not a very popular opinion, that I prefer this one over the original "Rec"; yeah this was was a rip-off and everything but the concept of a virus epidemic sounded better for me than demonic possessions; the ending of "Rec" was a real turn off for me because of this.
As for revealing nothing, the news articles in the end showed that some sort of an Armageddon cult was responsible for it. Anyway, I've never looked to be spoon-fed with explanations and conclusions while watching a movie; sometimes it's up to us, the audience, to make our own conclusions.
Anyway, as I said in the beginning you either love it or hate it. I love it, you hate it. To each his own!

That's one of the funny things about writing that fascinates me, that all the things we do for the audience are pretty artificial but people get frustrated if they're not there.

I'll tackle your paragraphs one at a time. I have to admit I did find the intro a bit cheesy and unreal. The opening party scene of Cloverfield felt much more believable. It'd be hard to do a footage film without this sort of intro though, see the characters in their mundane lives before hell breaks loose, I just wish it was a bit more natural.

You're right, I didn't get a huge feeling for who the characters were, or care about them, but I don't need to like the people in a scenario to want to find out what happens next, if that makes sense. While Jake was an interesting, likeable character, I liked it when he died if only because it subverted my expectations. He had "hero" stamped all over him so I thought it was gutsy to kill him off, I like having the cliche shattered.

I enjoyed the ending though. The best part of found footage films is putting the audience in the same frustrating, confusing, uncomfortable situation the characters are in. You only ever see the story from one POV so you're never going to get the complete picture, just like the characters (I rolled my eyes at the conveniently placed tape recorder they found, which also subverted my expectations when it turned out to be no help at all, heh). You're left thinking what the hell just happened, like most of the people that died. Although the hints that are there are enough to piece it together (in the final attic scene, with the doomsday cult clippings and the mouse cages and beakers).

And yeah I wouldn't say it was a horror film, although I find very few films horrific. It was very tense and rivetting, I usually enjoy found footage. Conventional cinema is very distancing, what with the clean camera angles and everyone speaking one at a time and "dark" rooms that are actually filled with a mysterious blue light coming from nowhere. I have nothing against that, obviously 99% of the films I've seen are like that. But sometimes I like a film like this where the camera is flailing wildly up the stairs and you can't quite make out where they are or who's with them, everything's out of focus and the dialogue overlaps. It's messy and...awesome. =P

The messiness is why it lends itself to horror/thriller/action type films. A found footage romantic comedy for example...haha, I'm not sure how that would work. It would be first person footage of him getting ready, walking down the street, turning up for the date. Not so great. It's the genres where the messiness actually improves what you're seeing, it reminds you that in that situation you'd don't have much more information than the characters do, you're just as disoriented as they are, it's not clear if the other characters got away too or if they're behind you or in front of you in the dark somewhere...all that sort of stuff.

Hmm, that was a long reply! So anyway, that's why I like found footage. The next step is to take out the "found" part and the "footage" part and just shoot a first-person movie.

That's why they call it...Hor(ror)ible