Right away, one thing I appreciated about Sherlock is that Sherlock Holmes (Benedict Cumberbatch) is almost immediately greeted by a disdainful female crime-scene cop as, "Hey, Freak." Because, think about it: Sherlock Holmes practices the art of solving crimes by "deduction". He takes one look Dr. John Watson (Martin Freeman), for instance, an Afghanistan War vet, who hobbles into a lab with a cane, and immediately figures out (with nary an exchanged word beyond introductions and, "Can I borrow your phone?") his Watson's whole life story as well as current living situation. As he unfolds and explains how he thinks (these are the most fun parts of the series), you can't help but express the amazement of the others, while thinking, "Is he some sort of freak!?!?"
Season One is actually a collection of what could be considered three hour-and-a-half self-contained TV movies.
"A Study in Pink" follows a series of suicides that turn out to be murders. The murderer somehow gets his victims to take poison... but how? This episode establishes the characters of Holmes and Watson, introduces them to each other, and shows how they become partners. The mystery-plot is interesting, and it is fun to see Sherlock and Holmes establish their testy and somewhat abrasive rapport.
"The Blind Banker", the weakest of the three, has Sherlock and Watson figuring out the meaning of a rash of deaths with a pattern of mysterious grafitti. Things lead through Chinatown and eventually the circus. This mystery seemed the most typical, and thusly the least interesting.
"The Great Game" picks it up again as it introduces the criminal genius Moriarty, whom takes a shine to challenging Holmes' problem-solving skills with particularly deadly deadlines. This one has a brisk pace, and you can also get a good sense that Sherlock's priorities of the fun of solving riddles vs. the potential of the loss of human lives is actually kind of messed up.
I've heard that fans of classic Holmes really enjoy this twisty modern adaptation. As a viewer going in without any frame of reference, I found this modern version fun and engaging, especially the winking acknowledgment of how Sherlock and Watson's relationship might seem, well, perceived as kind of gay in the modern world. Martin Freeman is especially good as the much put-upon, but totally capable Watson, and Benedict Cumberbatch must be doing something right, as his Sherlock is so pompous that he is borderline intolerable. Overall, it is a fun, lightweight reimagining of classic characters.