Just amazing, and magnetizing. The game will have you keep playing non-stop.
Pros
You have so much side missions, it isn't linear. You don't need to finish the story flat out. You can entertain yourself with them. So if you get tired of the story, you can talk to the townspeople, read the stuff and make choices.
The class system is great as well. You can choose a "solid" class, then it branches out to 2 or 3 sets of skills. Swapping weapons is allowed, which allows a feel of "control" over the character. If you get bored of playing your character, you can easily switch to one of your party members and control over them.
The tactics system allows the player to choose what the "bots" do as your party member. Exactly! You can choose if you want your party members to defend or attack, when to use a potion, when to use a skill. You have almost full control! This system gives the player opportunities to make killer strategies.
Challenging or not? I thought the game was pretty challenging. You can't just run in and kill everything you see. You actually have to plan out your strategy and utilize everything you have to survive. You have to make hard decisions, which may have bad consequences in the future. So beware!
There are romance options, you are allowed to have a relationship depending on how you talk to your party members and so on. There are "adult" scenes, if you are interested.
The pause system is quite awesome. You can pretty much freeze the gameplay and choose what your party members do, then unfreeze the game. Cool right? This feature also allows you to take screenshots at cool moments if you please.
Graphics are just amazing. My graphics card ATI Radeon 4650, can handle it at max settings.
Cons
You might think that you are leveling slowly. This could be very annoying, because the bosses will kill you almost instantly. I guess that's what makes it challenging, however, it's still annoying.
There's a lot of clicking, which is kind of boring over time. It's pretty much a MMO due to all the clicking. You may not feel a lot of "interaction" because of this. The thing is that this is made up by the story and the fact that you can pause and change control of the character you are playing.
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I loved this game, and it stayed with me after I beat it. I really recommend it, but note that it is pretty hard (for me at least).