The 'Normal' speed limiter, is tied in with Cruise control and will control the car, in that if you set a speed, lets say 5 mph above your current speed, the car will accelerate up to that speed and then maintain it, as long as required.
Touching the brake, or hitting the 'off' button will deactivate it instantly.
I use it for the vast majority of my motoring and as others have said, for maintaining speed limits, it's very useful.
Lane departure, is permanently switched off, also stop/start, when I remember!!
One of my pet hates is seeing rows of glaring brake lights when stopped in traffic, but don't get me started on lack of consideration for your fellow motorist generally, I guess it's the times we live in.