I think being unbiased is a good approach. I also was a bit sceptical when I was considering buying it because of the apparent extreme linearity of it. And when I played the other FFs, I did every single side-quest and played every single mini-game there was. I enjoyed running around towns chatting to NPCs and doing random quests (VIII was my favourite in my regard - so many side-quests! And not kill the monster ones).
So XIII completely cut this aspect out of the game. An aspect that I enjoyed. But I bought it and played it with an open mind. So here are some of my thoughts.
Character Backstories/Motives/Development: I would say that this is the best FF in this regard. All the main characters have well-fleshed out backstories, a sincere motivation for taking part in the plot, and they all develop as characters, realistically altering based on the circumstances that they face. And that is a refreshing change to modern FFs, where a lot of characters just tag along for the ride, with very little reason for them to be there. And they never develop as characters (Penelo from FFXII -> you are the biggest culprit).
Plot: The story is basically character-driven. So I think Square got the important bit right by getting the characters done properly. The plot at times can be unrealistic and over-the-top. But it is basically a prop to drive the characters on. And the characters are really top-notch. I think Loony Bob and I were discussing characters and he said that they all had depth - none of this one-dimensional rubbish. Some of them are cooler than others (Fang & Sazh for me), but they all are really good.
Villains: I thought they were good. I don't want to get into the details of it as I will spoil the game for you, but for me, the villains all believed they were doing the right thing. Which is quite invigorating, instead of the usual: I'm an evil person and I want power. So I would say that is similar to Vayne in XII. (SPOILER) And finding out that Cocoon was basically a chicken battery reminded me of the Matrix scene when Neo finds out that humans were being used as batteries. There are quite a few Matrix similarities I think
Linearity: Okay, this is not ideal. I like my FF games to be open. But I think that it worked out well. Maybe the developers at XIII were talking crap and the only reason it is linear is because of the work it would require to make it any other way, but they also mentioned that they did it to drive the story forward. If they did, it worked for me. But this is a preference and there definitely will be no consensus on this.
Battle System: Another thing where there will be no consensus. Put it this way. It's like an action movie. Very flashy, very stylish and very quick. But you end up being more of a general to your troops instead of the micro-manager you were in previous FFs. I quite enjoy this. I'm playing IX at the moment. The Festival of the Hunt where you have 12 minutes to hunt down monsters. Well, it took me 50 seconds to dispatch a lowly monster. And I seem to keep choosing the same actions. XIII automates this - fact. But I enjoy this automation rather than repeatedly pressing attack. That is an opinion.
But seriously, it looks really cool. Really, really cool.
I listed a whole lot of flaws in the flaw thread. There are some minor issues I found with it. But here is my final viewpoint on it.
Experience: Sometimes, XIII feels like a glorified movie. I will agree with that. You are kind of fighting to move the story along. I would say that every single FF has done this to some degree (and definitely since VII), but XIII is the most obviously blatant in this. But I enjoyed this story. And I loved the style that this game has. It oozes it.
So, I found the battles fun. In an over-the-top manner. People are going to argue that there is no strategy to them. I found that there was some strategy, especially in the timing. Another thing was that it is entirely possible for you to get defeated by most enemies if you are not paying attention. There are also movements forwards in that your HP automatically restores itself after each battle. I'm sure someone will argue that this is a step backwards, but I remember that in XII I just ran around in circles waiting for my MP to build up so I could cure my entire party before continuing. Sounds like a waste to me. Or continuously having to buy potions etc in every other FF game. Pointless stuff. Battles should be about battles, not how good you are at buying stock.
So I think this game has made progress in some significant areas, although like anything new, it is not perfect. I play FF for the story mainly. I enjoyed the story immensely. Therefore I liked this game. It is not perfect, it could be improved, but I liked it. And seeing this, I have great faith in Versus XIII (which has always been the one I've favoured over the 2).