The older implementations of LV tend to be very rudimentary, like just thrown into the camera just to say it had LV.. At least for my K20D it was pretty hopeless.
The newer ones should be better and closer to what P&S do, i.e. they "boost" the image, so 10 stop filters in strong sunlight, or even before sunset timing, should not be a problem..
So yes, it has made it easier to shoot long exposures, in some sense... Of course I could take out the filter and recompose through OVF, but it's so much easier to just mount the filter and compose.