I like Luke's whiny line about power converters, because he's obsessed with piloting and vehicles, and hanging out at Tosche station was the only thing close to a social life he has. He obviously was looking forward to any excuse to go there. Luke is supposed to be whiny, he's just a kid.
By contrast, Ani is supposed to be a Jedi (the best starpilot in the galaxy, and a good friend) yet he is more whiny and incapable of listening than young Luke.
There are some very small things I'd change about the dialog in SW. I'd make Carrie do another take of "I recognized your foul stench when I was brought on board" without the bad English accent. Must have been the result of hanging out with Peter and Alec. Han's line about the Kessel run should have been fixed because the use of "parsecs" makes no sense (it's a unit of distance). And a few of the lines could have been tightened slightly... "He tricked me into going this way" should have ended right there, for example. The dialog in the novel is way too wordy and the editing of the movie greatly improved it simply by removing words. They could have gone slightly further in a couple of spots.
One line that always bugged me (ESB or ROTJ?) was "it's not my fault!" which just sounded lame.