I rode all year on the 250 for the first 2 years of ownership. It was very sketchy during the winter to say the least. The stock tires like to skip a bit when its very cold.
Now I have a car + gained a bunch of weight because I'm no longer shivering.
Edit: Oh yeah, for tips we had a very good thread on this a while ago:
https://www.ninjette.org/forums/showthread.php?t=193270
In summary: Balaclava, pinlock visor, don't let the wind get to the trunk of your body, and for the love of god protect your hands somehow (heated gloves/barkbusters/etc).