Both. Depending on your situation.
Crutch - dark environment and unsure of shooters location. Laser gives you up. If it's a pressure switch you may have nerves running a mile a minute and not be thinking about it.
Useful - Dusk/dark environment and shooter/mugger close. Laser makes them crap their pants.
Doesn't mean you should trust it. Stuff happens, things go wrong, etc...
Personally I'm going to be buying a sub-compact with a laser because they're small and harder to aim. Plus the crap their pants thing. Lol
Really though, I do muscle memory drills at least once a week. Use your carry gun and practice with it unloaded, with snap caps. Start with just holding the gun by your side/waist. Quickly pick a target/object and snap the gun up fast to where you think it should be aimed and FREEZE.
Don't adjust your aim. Look down the sights and move your HEAD to line the sights up and see where you aimed.
Pick another target and continue. You should see yourself getting better. Once your doing OK...try the snap cap after you've aimed to help with trigger control too.
You "should" be good enough to hit a man sized target @ 20ft without missing from muscle memory. But I don't usually recommend live fire exercises