Went to see it today and quiet enjoyed it, through it didn't really blow me away.
Cameron's world is stunningly crafted, without doubt the best CGI in a film to date. I watched it in 3D, and as with other 3D films I've watched, I feel it took away from the experience and diluted the quality as the technology is still a little bit basic, and well, crap.
I loved the story, which was really compelling tale. So many layers and iconography, for someone who analyses and deconstructs films on a weekly basis, it was like a second Christmas :) Sam Worthington was really exceptional, as was his female co-star, Zoë Saldaña. Sigourney Weaver and Stephen Lang also gave very good performances, and I would say the entire cast was very good, aside from Laz Alonso as Tsu'Tey who just flopped as a result of him being 100% cliche and Giovanni Ribisi as Parker Selfridge who had no characterisation whatsoever as far as I could tell ^^
In review: good, detailed and multi-layered plot, brilliant casting/acting, stunning visuals but if you want to really appreciate them, do yourself a favour and go watch it in Digital, not 3D.
Wow, that was LONG... ^^