What makes a short story sweet?

Short fiction. Concise, pointed, generally fast-paced. But what makes short fiction Short & Sweet as opposed to just plain Short? I’ve read quite a cross section of short fiction throughout my years of primary school, high school, personal reading and now university. And quite miserably, for every good short piece of fiction that I’ve enjoyed, I’ve had to endure approximately five terrible pieces. The art of short fiction is apparently one in its own right and those who think you can just cut a chapter out of a novel have yourself a short story are very, very wrong. Short stories require quite a bit of coy plotting for although it may not take as long to write and think up as a five hundred page fantasy novel, you have little room for whinnying your way around to the point. You have to get there. Fast. But still with enough padding that you can call it literature as opposed to an assembly of dot points. 

So, that all said, what are your thoughts on short fiction and what makes it good? What do you like to read and what do you think a writer has to do to serve this genre well?