You shouldn't be braking when changing lanes is what I was taught, you should be matching the speed of the lane you're merging to. There are many drivers who think that braking is always the right solution, when sometimes it's a little more gas.

And in inclement conditions, it can make the difference between losing control of your vehicle or not. When you brake, you decrease your steering ability in most cars. Fine when its calm and sunny in CA, not so much when it's icing over near Ashland OR on the pass.