Saw it yesterday. Surprised and impressed that the cinema (medium-sized Vue screen) was almost full so long after the film's release. Also surprised that the audience, whilst seeming gripped throughout, didn't get the film's humour. Admittedly the humour is very dry, with The Ghost getting a lot of one-liners, but I found it funny.
It's well-directed, the tension is kept up and although the twist is guessable it's not obvious from the start like some films (step forward, Shutter Island). It's very much from a particular style of film-making, maybe some people used to fast action films will find it boring but I was totally gripped by the atmosphere and the sense of unease that Polanski is so adept at creating. Not giving anything away but the ending relies on a message being passed from one person to another and the way it's filmed is almost Hitchcockian in the way it uses a small, inconsequential action to build tension. Good stuff.