So I'm listening (again) to the Star Wars Radio Dramas. I really do enjoy it. I agree that there are some scenes that are unnecessary, but since it was released as weekly episodes, this may have been less of a problem. Several of the scenes are really interesting and add to the overall story, so I have no problem with those.
I really enjoy having Mark Hamill and Anthony Daniels there. I think it helps keep the familiar feel. I really enjoy the Obi-Wan actor (can't remember his name), and feel that he does a very nice job. Ann Sachs is a very good snarky Leia. What I find interesting (and was noted earlier in this thread) is the very different Vader and Han actors. Vader feels very different, more subject to his passions. The Prowse/Jones film version always seems very angry, but always in control. The radio version seems more willing to lose his temper and lash out. His voice is less intimidating, but I think earlier posts nail it that he feels more like a classic villain. Han feels even more different, where he comes off as a bigger jerk. His voice is more reminiscent of an arrogant high school punk. At first he was quite startling, but I'm surprised how well I could settle into this very different Han. I don't like him better than Ford, but I can't say that I like him much less; he's actually a pretty interesting different take. Let's see, I also like the Biggs actor, the Tarkin actor...man, I guess I just really am surprised how well I enjoy the radio drama. I'm nearly done, so I'll be starting ESB soon.