The friction of snow is almost the same as the friction of sand. No, it's not dangerous. With ice you need some studded tires. There are some good tires from Schwalbe (Marathon Winter is my favorite) or Suomityres (ex. Nokian)

Few years ago I made a weekend trip on the sea. (Yes, it was frozen ;-) That was fun. No hills. Just the endless ice.

[edit]Just added a photo from that trip to my avatar. As you can see, the views were mostly gray ;-)[/edit]

Jussi