For someone who likes sci-fi I don't spend enough time thinking about long distance space travel.
I admire the stories that avoid "warp drives" or "worm holes" -- though such a thing isn't a dealbreaker. I just think it's admirable to deal with the upsetting immensity of space on its own terms.
But if you want to avoid hand-waving you need to really think about how people deal with time, delayed communication, etc.
What is your favorite way that a sci-fi story did "long distance" ?