The look of it; don't get me wrong as a piece of engineering it's a fine car but if I owned one it's not a car I'd walk away from after a drive and feel any compulsion to take a second look back at. Ay least the Mk1 isn't as goppingly houndish as the Mk2 which looks like it's suffered a severe stroke.
I had written "(apart from the fact it's supremely hideous)" but then deleted it! I totally agree that you would not want to spend any time looking at it, but as long as you could locate it and get inside it with your eyes closed, it wouldn't be a bad place to spend some time (apart from people looking at you\the car in disgust).
I am really struggling with the MK2 1 Series too, cos on paper the M135i sounds like the perfect replacement for the S3. But it is really really ugly!