I thoroughly enjoyed A Study in Pink. I thought it was a very good adaptation of Sherlock Holmes, and it worked remarkably well in a modern setting.
I thought the story worked really well as a mystery, and it incorporated modern technology very well (I can't quite decide whether Sherlock should love or despise the internet - probably both).
All of Sherlock's deduction techniques were present, and it was very fun to see the bits of his thought process as he looked over the woman's body. It frees the story from the post-discovery expositions, but still lets us know exactly what he found. Similarly, I liked the run through his memories concerning his first deductions about Watson (and was amused by Harry being a woman), and the projection of London's map in his brain.
I quite liked the beginning, as it is pretty much taken exactly from A Study in Scarlet. Not only Watson's backstory hasn't changed, but their first meeting is nearly identical (although the reading of Watson's phone is originally done with a pocket watch at the beginning of The Sign of the Four). Which I know is not very difficult to do, but it still appeals to my fan side.
I started to re-read Scarlet, mainly to double check exactly how identical the beginnings were, and found that many elements are common to both mysteries. Both feature an empty building in Brixton, the victim has been poisoned and is lying face first on the floor. Both have RACHE, but while in Pink it was indeed Rachel, in Scarlet it was revenge. Both have two pills from which to choose, and a dying cabbie as the murderer. The main difference is that the murders in Pink are random, while there is a very clear purpose to the murders in Scarlet.
Although overall I really enjoyed it, there were a couple of points that I didn't like. Lestrade was characterised a bit in the incompetent side, while he is genuinely a good, competent policeman. Mycroft was done a bit over the top. Sherlock too simply too long to make the taxi driver connection. Alex figured it out at the "who do we trust" speech, and there was no doubt left when the random cab appeared. And yet he didn't obviously get that. I'm willing to let slide, just this once.
I will be watching the next one. If they keep being good, it will be a shame that it's only three episodes!