I'll start with my complaints.
Mostly it's Nemesis.
Its original form is fine. An updated version of the original. No issue there.
However, it's later in the game when it mutates to stage 2 that I really didn't like the design.
Instead of keeping it humanoid they wen't for an animal, quadruped design and at least doubled its size.
IMO, they could/should have kept the humanoid design, but let the tentacles overgrow and given it new abilities.
This design carries on throughout the rest of the game, and even shows up in an altered version of the waste disposal room fight.
The final battle is super ridicules and reminds me of the over the top set pieces from later RE games.
Even the rail canon seems out of place here and more fitting of the blockbuster set pieces of RE 5 and 6.
Basically, when Nemesis starts to mutate, the game loses a lot of its subtlety and falls apart a bit for me.
Now, the changes they made to different areas, dropping some areas and adding new ones was done really well.
Firstly there's the clocktower.
It doesn't appear in full, but it's the battle ground for fighting the Nemesis stage 2.
Aside from my dislike of the stage 2 design, the battle and its arena were spot on.
If the traditional stage 2 design(basically a more damaged version of the stage one design) had been used, the only changes that would have needed to be made to this version of the clocktower would have been the addition of a few obstacles to make the arena more enclosed.
The next change was the RPD, as you don't visit as Jill, but instead play as Carlos going there for part of a mission with the UBCS, which incidentally is another great addition to the game, adding in more depth to these guys.
The hospital has also been expanded and leads into a new version of the final area, formally the disposal facility, now NEST 2, a second underground lab.
Everything in these two areas feels more involved and has some traditional back tracking.
There are also a couple of additional areas like the underground/sewer sections, the first of which leads to the first real Nemesis boss fight atop an under construction tower.
The second sewer section links events of the subway train to the arrival at the clocktower.
Both of these are well thought out and more than make up for the removal of areas like city hall and the newspaper offices, adding more variation.
They also replace the park area which would have linked the hospital to the disposal facility.
Obviously with the removal of the park comes the removal of the gravedigger giant worm boss battle.
Honestly, I didn't even miss it.
For me, the park was a bit of a dead spot in the original, and the remake has moved some of the story elements revealed there to other parts of the game.