Dedicated snow tires and drive very carefully and you can do fine in the snow. I havent driven an IS in snow, but from 1955 through 1986 all we ever had were rear wheel drive cars and it was just routine to put on snow tires every fall. More recently I got caught in a snow storm up near Cleveland in my 94 Firebird with all weather tires. Old driving habits kicked in and I did just fine. The only thing that held things up were three wrecks along the way, all front wheel drive vehicles, by the way. Its all a matter of good tires, careful driving, and knowing how to correct a little skid when it happens. Following distance, speed, brake moderation, and trying to maintain momentum before you get to a hill or whatever are key.
I might add that the only two cars I ever spun out in snow were a Fiesta and a Escort, both FWD cars. If you start into a turn with FWD and the front wheels spin, you end up with no steering and the car tends to plow in whatever direction it was heading at the time. Personally, I'd rather be in RWD as you can at least take action to correct a skid with it.