I'll keep this short and sweet. My wife and I saw it a few hours ago and enjoyed it. But here are a few things to expect...
Predictably, with Beyonce and Childish Gambino playing the adult Nala and Simba, you already knew the singing was going to be twice as soulful as the original 1994 version. Beyonce began riffing with her first note. They didn't over-sing as much as you'd think, but you can't help but notice the ad-libs.
Modern slang is added to the dialog, including phrases like, "I got this."
A new scene is added to the story.
As I hinted at earlier, James Earl Jones' voice has certainly grown weaker as he aged. Mufasa's voice is still deep, to be sure, but lacks the BOOM and presence of 1994. As a result, Mufasa's character seems a bit more passive and less authoritative this time. James Earl Jones is 88 years old now, and is (to my knowledge) the only person from the original cast present in the reboot.
Lead Hyena Shenzi is given more screen-time this time around and shows much more menace. You could argue that she's even more dangerous than Scar, and she's far less submissive to him than in the original. She's a horrible villain in her own right. (Whoopi Goldberg played Shenzi originally. This time the character is voiced by Florence Kasumba).
While Shenzi's role was elevated this time, Rafiki''s role was reduced noticeably.
The CGI was actually pretty decent in my opinion. People have complained about the "lack of emotion" from the CGI animals. Of course lions can't smile or anything, so this was to be expected. At times their expressions were blank, but in key emotional scenes, their faces had great reactions.
Overall I enjoyed it, and aside from the few things I mentioned here, there isn't much to say. Of course nothing will top the original. The Lion King is like The Wizard of Oz of my generation. No reboots, sequels or add-ons will come close to capturing the magic of that 1994 Disney Masterpiece. The story flowed pretty well, and even the small amount of people who may see this one first before the original will be able to understand the story easily. In this writer's opinion, it's definitely worth checking out.