You would think that they would have their new toy surrounded by a fleet , but then where is the fleet when the rebels attack? If that sort of fleet was available then the rebels would have been toasted.
I think it then makes the finale seem less believable if you show that sort of firepower in ANH.

I don't think there is even a need for the planet at all, it looks very very cool but I liked the idea that the DS was off in deep space hidden from the eyes of the world(s).
Also those conversations feel more real to me if they are taking place out in deep space rather than while kicking around in orbit - don't know why but they do.