I have watched the first six episodes and I'm really enjoying it, so far. I'm not going to do any kind of in depth reviewing because I just don't have the energy for it right now, but when the season's over I may do a kind of retrospective so I can pick out favorite moments/episodes and talk about the season's arc. (Votes yay/nay?)
Edit: I do speculate as to what they're doing with the season, it might be considered mildly spoilery by some so if that bothers you: FLEE!
I like what they're doing with Sherlock and Joan as characters, especially with how they interact. The character bits are all wrapped around a fairly middle-of-the-road procedural, which is fine by me as I like procedurals in general- and the cases have gotten better, more interesting and more complex as the season goes on. I think they were easing into it.
I like this take on Holmes. He's approachable, he's capable of warmth and humanity and even (bad) practical jokes. To make the natural comparison: I can't see Cumberbatch's Holmes hiring someone to trick Watson for lolz. The Holmes from BBC's Sherlock is accused of being a machine, you could never make the same accusation for Elementary's Holmes.
I love Joan Watson. I like how she's so willing to work with him when he needs it, and how unflappable she can be when she's sorting through methods of working with him. She will also totally call him out for bullshit- she is being paid not to put up with certain things, so that makes a lot of sense. She's incredibly competent and it's clear that she's very smart and is already picking up on his deductive tendencies. I love how they interact, I love that there is something of a patient/doctor relationship right now, and I love Lucy Liu in this role. (I love Joan Watson and want to marry her.)
I also have what one might describe as a 'headcanon' for this particular take on Sherlock Holmes (although really it's more of an educated guess). We see, in the first episode, that Sherlock keeps bees. He's working on writing a book about bees. We know that, according to the canon, Holmes retires to the country with Watson and raises bees, and he writes the book that Elementary!Holmes cites as working on in the pilot episode. Episode six ended with Joan asking Sherlock about Irene, so we know that Holmes has already met Irene Adler.
What am I getting at? I believe that this series is taking place AFTER canon, essentially. Because Elementary!Holmes did not have a Watson in London, he was muddling along on his own, and things clearly Did Not Go Well as a result. What happened is going to be revealed (and is liable to be a good chunk of the story arc for the season) but I suspect that, without the companionship that Watson provides, when things started going bad for Holmes they went REALLY badly because he had nobody to steady him. I believe it to be possible that he's had a run-in with Moriarty as well, though I doubt Moriarty is dead as yet (and it's possible that Sherlock's wicked drug bender got him out of London before he could start really pursuing Moriarty).
I think it's a really interesting choice that could yield some great fodder for character development while still staying away from Sherlock territory. This show HAS to stay away from Sherlock territory, since they failed at getting the rights to adapt Sherlock the BBC are keeping a close eye on the show to make sure it isn't swiping. I feel like Elementary has put enough of their own stamp on these characters that it's clear that they aren't swiping.
I could be wrong about my interpretation of what is going on, we're only six episodes in and that's just not a lot to go on, but I'm really enjoying it either way.