One significant thing to remember about riding against traffic is that NO driver will ever be looking for you there. Remember, BY FAR the most dangerous place on the road is intersections. When a car comes to an intersection to turn right, what does the driver do? He looks left, and when the way is clear, he goes. If he looks right at all, it's a cursory glance, and as any cyclist can tell you, even a driver that looks right at you probably doesn't see you. If you were proceeding through the intersection, you're gonna get T-boned.

Same goes for riding on the sidewalk; when you come to intersections, no car driver expects you and you will not be watched for.

Also, since you're riding illegally, you have NO standing legally if you get hit. Whatever damages you get are probably not going to be covered by the other guy's insurance, and you've got no chance in court.