My overall first impression is very positive. Most significant, I loved the fact that Bilbo is portrayed as a sane, reasonable, and mature adult. My biggest complaint about The Lord of the Rings (LOTR) movies is that the Hobbits come off as young and stupid, when in fact they were all grown adults, and two of them were men of substantial property. In The Hobbit, Bilbo is a multidimensional character and very much an asset to the dwarfs' party.
I had my doubts about how Jackson was going to manage to create three movies from one short book, but I liked where the first movie left off and was pleased with the additions to the story. Jackson maintained some of Tolkien's humor but didn't sugar-coat the battle scenes, creating a great balance.
In addition, I was pleased to see the returning actors, which preserves the continuity with LOTR. The sets too were consistent with the first movies, and I enjoyed seeing familiar places (Hobbiton and Rivendale) from new perspectives and angles. Finally, the acting, special effects, and scenery, were--as I expected--spectacular. Oh, and Jackson wisely left out the slow-motion scenes that I so hated in LOTR.
Just to clarify: I have seen the LOTR movies multiple times and own the extended BluRay edition. I didn't hate the movies, but I had issues with them. So far, I have very few reservations about The Hobbit, and recommend it to fans of the book.