I finally saw this last night with a group from my office. Saw it in 3D unlike my one and only theatrical viewing of the original movie. I am a sucker for James Cameron's science fiction efforts. I love his depiction of hardware of the future, and how he grounds it in the familiar even when the movie is set in 2159 (don't know that date is the fact, but I believe the original was 2154 and this one was 5 years later).
Visually, this movie is spectacular, as was the original. Clearly, this was a movie that was likely as close to 100% visual effects as any ever released. I have read nothing on how the effects were produced, but am presuming a lot of CGI was employed. There were many scenes that for my 55-year-old eyes appeared to be a bit off. The rendering was great - none of the characters appeared like young Princess Leia in Rogue One, for instance, but I just felt that the color spectrum was a bit too vibrant, cartoonish almost. That is a minor quibble that may very well be only in my eyes.
I cannot say that the story truly wowed me. It was largely meh for me, but it was a vast improvement upon the previous movie. I don't have a derisive statement to make about this one as I have for the first (Dances With Wolves in space, or something similar). I do get why the colonel was returned as an avatar, as his mission to kill Jake Sully drove the entire narrative, but just felt like a "getting the gang back together" approach. No, I don't have any alternatives to how Cameron could have developed his story. The colonel as an avatar is fine but IMO a bit lazy.
Regarding the 3D, I was amazed at that. Despite my issues with the color spectrum, the 3D gave that entire world a sense of being alive. And holy crap, when tracer fire was on screen, it literally appeared to come right at my chest. Same with splashes of water.
When it ended, I told my wife that Cameron had finally found a way to meld Aliens with Titanic and maybe a bit of The Abyss into his Avatar world. The scene were the youngest daughter and the Gamora gal's mom got sucked down the hole while the attack ship was sinking gave me an instant flashback to Newt falling down the chute with Ripley failing to pull her back by her jacket in Aliens. And of course the mom/daughter crawling through the upside-down cafeteria looked like something one might have seen in Titanic.