I drove with it on last winter, it's off this winter. Never thought of the plastic cracking, I can't remember too much ice building up between the roof and the basket.
The real pain was the rapid melt and overnight freeze I remember. The melting snow would create a frozen waterfall over my doors and windshield. I have less use for it during the winter months, plus it's a little easier when I want to give my X a quick wash from the salt. ( remember to put the screws back in after removing the basket )