Honestly I feel like there might be two different movies out there, because I didn't see the one these glowing reviewers did!
The good: It was a very pretty movie. The cinematography was nice, and it seemed well-made. The score was lovely, as well. I was able to watch the entire thing without shutting it off, so it wasn't the worst I'd ever seen. I liked one of the characters, and genuinely felt for her at times. I liked the premise, it was an interesting situation. I liked the uncertainty of whether it was paranormal or psychological, though I think they could have pressed that further in either/both directions.
The bad: The movie was needlessly gross, with unnecessary amounts of maggots, puke, and diarrhea. I have a strong stomach, so it didn't bother me so much as it made the whole movie seem like it was trying way too hard. Two of the three characters were pretty one- dimensional, though it was clear the writer tried very hard to add depth with a weird backstory that went nowhere. The other character had almost no dialogue, and was mostly seen laying around. Some of the dialogue was very cheesy, it was impossible not to notice that they were going off of a script. The plot was completely unfocused and felt incomplete. There was lots of gazing off mysteriously into the distance, which seemed like an attempt to come off as artsy but ended up feeling vapid.
Also, I kept seeing ways to escape or get help that they didn't address. The water was turned off from within the apartment, surely a pipe could have been broken open (which, by the way, could also have attracted the attention of the caretaker); they could have built a fire on the balcony to signal for help; there was plenty of fabric and clothing around to create another rope after the first one was dropped; they could have shimmied down the rope to the apartment below and repeated, there was no need to make one long enough to reach the street (dangerous, but surely a better option than murder and cannibalism, right? Not to mention another apartment might have more supplies and/or an unlocked door); etc.
There were also lots of questions I had. Why was a spider still alive under the glass after all that time? Why would you scrape a glass along the bottom of the tub instead of drinking from the source directly? Why did their teeth go completely rotten in what was presumably about a month? Why were there so many maggots? Why eat spiders and human flesh, but not the maggots, which would actually have provided protein? Why would an entire building be shut down and still supplied electricity and water? Why would an entire building be shut down like that at all? Shouldn't the "caretaker" have checked to make sure the building was empty before going around locking all of the doors? Was there no fire escape? Why did the guy have the strength to rape two women and not to fight for his life (you'd be surprised what adrenaline and the body's response to choking can do)?
Also, uncooked pasta is delicious. One of the characters made a fuss about it. I know that's not a real complaint, but I wanted to include it. :P