My original review of the theatrical cut can be found here. For this review, I watched the 179-minute extended cut. It's still the same movie. Most of the new footage is just little bits and pieces, a bit more action here, a longer flight there. There is a six-minute prologue that takes place on Earth, which establishes the environmental damage that the planet has sustained, while also establishing Jake Sully (Sam Worthington) as someone who cannot walk away from someone in peril. It's a bit broad, but it gives us a rooting interest in Sully beyond him simply being the lead character. There are extra moments for Grace (Sigourney Weaver), including a more detailed explanation of why her precious school for Na'vi ended up closing. There is a very brief (and non-explicit) sex scene between Jake and Neytiri (Zoe Saldana). The other big change is a very different finale for Tsu'tey (Laz Alonso). Oh, he still gets his powerful final stand and subsequent death plunge, but... well, you'll have to see for yourself what happens afterward. It's an interesting addition, but I kinda liked the haunting original demise.
None of the additions radically affect the movie. It's still a ripping adventure story that works on a visual and emotional level. The second act still drags a bit, but the pay off is more than worth it. I still love Saldana's fiercely emotional work as Neytiri. I still love the climactic action sequence, a stunning piece of work that rivals the epic warfare in Peter Jackson's The Lord of the Rings and John Woo's Red Cliff. I still love how company man Parker Selfridge (Giovanni Ribisi) isn't quite as one-dimensional as he appears (he's clearly bothered by the collateral damage, just too weak to do anything about it). I love that the entire film is edited with long, fluid takes that puts the 'put your film in a blender' editing from Paul Greengrass or Ridley and Tony Scott to shame. And for the record, the film works every bit as well in 2D on Blu-Ray as it did in 3D IMAX theaters. Heck, since the film was shot in 3D by someone who knows what he's doing, the entire film has a three-dimensional quality that almost makes it feel like 3D. Truth be told, the only time you miss it is during the occasional obvious 3D bits (creatures flying towards the camera, etc). Avatar was never the greatest film ever made. Sully's on-the-nose expository voice over is more annoying than ever (most of the cheesy dialogue is from the voice over), while Norm Spellman (Joel Moore) and Trudy Chacon (Michelle Rodriguez) are basically irrelevant to the story. But it remains a visually beautiful adventure story with just enough social relevance to make it matter. It's still a damn good movie.
Needless to say, all three cuts on disc 1 look and sound superb. If there is a flaw, it is that the ultra-bright richness of the image diminishes the photo realism that the darkened 3D image helped sell in theaters. But if you simply accept that what you're seeing couldn't possibly be real anyway, it doesn't take you out of the film to any real degree. Oddly enough, the relative simplicity of the core story allows repeat viewers to just scan the image for any number of details that they missed the first time around. It helps that most of the exposition is in the first act, which mainly takes place away from Pandora, which allows viewers to just drink in the visuals in the second and third acts. Assuming the lack of 3D isn't a deal breaker, this is a stunning image. Oh, and Fox earns big bonus points for allowing viewers to simply skip to the new footage in either of the longer cuts, for those who just want to see the new stuff.
Now about those extras. There are a total of just between 7-9 hours of video-based material on the second and third discs (there's a 65 minute feature on disc three that can be watched three different ways). Best of all, there are no unnecessary bells and whistles. It's 7 hours of deleted scenes, marketing materials, and hardcore behind the scenes footage. Plus, you get 15 photo and art galleries (costumes, weapons, locations, etc) and two versions of the screenplay (the original 'scriptment' and the final shooting script). The main attraction is the 67 minutes of rough and unfinished deleted scenes, which adds up to 28 scenes totaling about 45 minutes of new footage. I won't do a run-down of the scenes, as I imagine anyone who wants to buy this disc would prefer to discover them for themselves. But I will note that the best new stuff is from the human characters. We get more guilt for Jake, and more moments of shading for Parker, including a climactic confrontation with Quaritch (Stephen Lang) where he basically attempts to stop the coming genocide. You also get a climactic bit for Dr. Max Patel (Dileep Rao), who in the finished cuts basically vanishes at the start of the third act. I'm not sure the world needs a four-hour cut of Avatar, but there are any number of character beats in this batch of footage that would have improved the picture.