Bingowings said:

If they are cutting edge why don't the Imperials fly them?

There is actually an explanation for that in EU. But you can stick to the film to get the explanation. Rebels had some powerful supporters (Leia for example) and the galaxy is big. I don't see why they couldn't develop something in the secret.

Let me throw you another bone since I think this one is worn out. :)

You know, I think Han loved C3PO. Besides picking him in ROTJ, the crucial evidence of that is in ESB. He actually for some very illogical reason bothered to pick him up on Hoth when he could have just left him there. He even came back and opened the door for him. :D