I still haven't actually finished it yet, but it's a damn impressive game. I've seen estimates of around 40 hours to get the platinum trophy which is a bit shorter than current AAA RPGs, but it's still a satisfying run. There's a LOT of extra story and content, so don't expect it to be a faithful recreation of the original. For context, I ran through the part of the story covered in the Remake in the original game first. In the original, it took me approx 6 hours from start to stopping point in Remake. So add in an extra 44 hours of gameplay and story, extra characterization, more context to the AVALANCHE characters so that you get more attached to them.
There's weird extra story that wasn't in the original that seems to have divided the community but personally I really like the additions.
The graphics are top-notch. It feels like playing 40 hours of interactive Advent Children.