It is visually great, and the scenes where SJ's character meets new "acquintances" are all gold. There were a few where I wasn't quite sure if we were watching the untrained locals or paid actors. The beach scene is really creepy. SJ is brilliant, a great pleasure to see her do something almost opposite to those bloody Avengers movies!
The fantasy scenes ... well, just what was the point? Over my head I suspect, but great 'cinema'. The film might have worked better with JUST the naturalistic scenes, the other stuff could all have been done off-screen. We get all these hints about what she does to the men, and about her weird motorcyclist guardian(s) - but I was left with too many Qs. What is her guardian's job? Does he need to 'feed' (or whatever?) Why bother with all the seduction - why not just kidnap the blokes? Did she need their help to feed? Is she in charge? I could go on ... I expect none of these facts are important, but they were a constant distraction.
I suspect they just wanted some cool shots of a motorbike hooning along dark snowy/wet scottish roads - box ticked!
What "story" was this telling? Something about an alien viewpoint , blah blah ... I really didn't feel anything new or interesting there.
I was rather disappointed that the accent SJ perfected for this turned out to be cut-glass English, not Scottish as I'd hoped for! I can see why they chose it though - she would have been much less 'alien' to the locals otherwise.
The "making of" story has a few interesting twists:
http://en.wikipedia.org/wiki/Under_the_Skin_(2013_film)#Production