Sherlock definitely accomplished what it set out to do - to update Sherlock Holmes and his surrounding myth to the 21st century. Benedict Cumberbatch and Martin Freeman were good enough as Holmes and Watson that I wondered vaguely how they'd do in a period-costume version, although Holmes's nigh-sociopathic callousness was maybe over-emphasised - the original would at least observe the social niceties when interviewing a distressed client, and would sternly declare his opponents to be abominable before diving into the clues. Maybe someone thought that this was just a mask, and a modern Holmes wouldn't bother. Meanwhile, the scriptwriters had enormous fun working stuff from the original stories into the modern-day version, doubtless seeing how much they could include that would make the people who just think they know Holmes accuse them of gross distortion before the people who've actually read the stories jumped in to point out the truth.
But oh dear, it was rushed. I got the feeling that the writers wanted a full multi-week series and pitched a story arc on that assumption - and the BBC said "great, you can give us that in three 90-minute episodes". So in the first episode, we got the Big Meeting and the basic relationships framework, and Holmes heard the name "Moriarty"; in the second, Holmes cracked a case (with the aid of one stonking big coincidence, if you were paying attention) and unbeknown to him, the leader of the villains was collaborating with someone who signed himself "M" and who employed a sniper (doubtless name of Moran), and in the third, Moriarty decided that Holmes was both threat enough and entertaining enough that he gave him an episode's worth of arbitrary puzzles at huge cost to himself and his credibility, then emerged from the shadows to reveal himself to be a bit of a loony, eventually setting up an arbitrary To Be Continued.
Okay, now BBC; it works, okay? That much should have been obvious from the first, but anyway, if you're prepared to believe it now, give Moffat and Gatiss at least a dozen or so episodes to expand into, let them wrap up the Moriarty nonsense with one mighty bound in the first (Moriarty was always a dull and cumbersome element to the original Holmes mythos, after all - making him a big feature of the modern version was a bit lazy), and let's see Cumberbatch and Freeman weave their intellectually sinuous way across modern London the way that Jeremy Brett and Edward Hardwicke made Victorian-Edwardian London look so damn good.
Otherwise, don't bother.