I never freaking knew that was a hotkey. However the problem is that sometimes when I click on the airbrush and find that the cursor is set to Precise. I would go to preferences and find that it IS set to Brush Size, I would then click Precise and it would go to Brush Size!
Oh wait a minute...(The fog is clearing...)
Ok the preferences only has to do with what settings Photoshop loads up with. So if the cursor is set to brush size, It will be Brush Size when PS loads up. But if you press CapsLock and set it to Precise and then check Preferences, it will still be set to Brush Size.
DOH!, my brain hurts now. That drove me nutz for years.
Thanks ppl, I will try to keep my pinky off the friggin CapsLock.