My post might be very different since I've only completed the original version of the game. However here's a link just incase you would like to see any of the differences. Some are not exactly important in there, but it's there:
http://finalfantasy.wikia.com/wiki/Final_Fantasy_XII/Version_differences (Should be a little down when you scroll on the site, Zodiac Age is basically International Zodiac Job System except the PS4 version has a better titled name and running on a better console, along with some new features to enhance the game's normal output of boredom like 2x speed etc.)
1) They were enjoyable to explore the first time, but may not be the same type of fun/interesting the second time seeing as this game was already released ages ago (for returning players), but we are just now getting this version after so many years. Upon further checking, this is literally the "real" version we were suppose to have awhile back. Course this is a matter of taste but some of them were fun to explore (at the time). The game is definitely nowhere near FFXV's potential on capturing the eyes seeing as this is just an enhanced port from a older game, but it was fun.
One of the best parts of the game is the "end game" quests, not the early ones because those are a chore. The monsters were quite a surprise because there is a shit ton of them where they are all different (on a fair note, there are monsters that are usually reskinned from another monster in a different color or just enhanced in size). Treasures in the game were seeked out by players, but nothing totally of huge value except the end game treasures.
2) Random encounters with wild enemies weren't exactly annoying (actually it's not really random encounters but eh they are in the wild), but can be an issue going to an area you are not suppose to be in yet. In fact, one of the stuff people had issues with (same for me back then) is that the level spikes pretty big when going to a new location that the game tells you to go. For example, the game will tell you to go to this X forest here, but you must cross this desert first of level 15 monsters to get to this forest. Ok cool that's fine, but when you actually make it to the forest the monsters there are level 25 while you are somewhere within the 18 or 19 margin. The game spikes in odd ways that makes you grind for EXP and this can be somewhat brutal with boredom because it takes a bit of time. Luckily Final Fantasy Santa came in to the rescue and whispered Square to add a 2x/4x speedkick to kill this boredom because let me tell you, it was kinda of a drag on the original version.
3) There are very few cities that are explorable within Ivalice, Dalmasca is a popular one. I'll have to get back on you with this since it was a long time that I played the game but I do remember the map layout is mostly long corridors type maps with buildings you can go inside into another loading screen. If I had to put it like this, it's not like The Witcher or Assassin's Creed free roam of expanse, it's more like a big city with layers and wings and each wing will have a line spot that takes you into the next big wing.
4) The combat is debatable, but if I had to give an honest answer. It's an awkward battle system (at first).
Within my experience, the combat was incredibly slow at the very beginning and boring because you don't have access to those skills that makes the battle much more enjoyable, not to mention that the battles take a bit longer compared to most of the other FFs due to the active gauges filling up to commence another action. Not only just the battles at first were boring, but the entire kick start of the story in the very beginning and adventure was just so boring. The game literally does not start getting good until you pass 15% (an estimate, not exact) of the game. In fact, I may just tap in that 2x/4x speed to skip pass the early stuff because it was really ugh.
5) The raw story of the game caps an estimate around 60+ hours depending on the player's time and how he progresses, but that's usually a rough estimate for people who just keep on playing, and then a raw total for everything is roughly 105+. For those completionists players, somewhere 120+.