Well.. if the BG hasn't seen you, then there's a posibility your position is not yet known esp if you hide behind cover. Once the BG sees the beam from your laser, your position is already compromised.
I'm neither for or against lasers. I've never had them on my carry weapons. Like any other accessory they have their purposes and advantages when used properly.
In low light shooting, this can be an advantage or disadvantage. Only you can really judge for yourself if it will be helpful for each particular situation. If you practice enough with it, I'm sure it can be very helpful in the dark.