IIRC, the radio drama invented a reason why Threepio was so annoying in ESB.

In hindsight, Empire is nowhere near as dark as say, Episode III. The fun is still there if you look for it. The audience was three years older, and a lot of imitators had come and gone in that period.

The pressure was on the filmmakers to deliver a story that built on the first, but not rehash it as many sequels to other 70's blockbusters ultimately did. That's a trap that even Jedi arguably falls into at times.