Depends on the moisture content as Lister says. Water droplets landing on a subzero airframe isn't nice. Also, flying through clouds in subzero conditions is asking for trouble.
That said, my aircraft loves it when it's cold. Gin clear blue sky, nice cold dense air and low humidity - wonderful.
If you're in a 150/152, look for ice build up on the leading edge of the strut, that's where I notice it.