Many critics have given the film high praise! Mark Kermode tweeted that he's firmly in the LOVE camp.
I saw it last night, and as suspected some of the confused critics from TIFF mis-read it because they're astonishly dense about class (honestly, they keep describing Laing as a man who fits in with the upper floor residents and the lower floor residents - this is not true at all, he is kicked out of the penthouse party!) and expected a conventional story structure. The Snowpiercer comparisons are way, way off - it's nothing like Snowpiercer, which has a logical structure and premise. High Rise is not like that at all - it's a darkly funny satire. It's absolutely batshit crazy and doesn't attempt to be accessible or logical.
It's a dream-like experience - time is compressed into montages, we jump around from event to event and floor to floor, and people do things that are simply bizarre as if they're completely normal.
I loved it. Not everyone will, though.