about decelerating - can't you do a lot of that just by going in to orbit around something big when you arrive (and switching off the thrust ofc)?
But what do I know?
Presumably you'd have to have another means of local manouevering anyway?

And maybe you sometimes wouldn't even aim at the star you were heading for. Maybe sometimes it would be better to "slingshot" round something else on the way, where you could lose, or gain, momentum.

And couldn't you steer a bit with angled deflectors? (as long as the beam moved with you ofc)