I finished this game last month and think this game is pretty good. Linearity isn't a problem for me. I actually like it linear because it's very convenient and it's also easy to get more or less all available items.
Story is fine, at least decent enough to sustain my interest through the game. The difficulty is well tuned for my taste. Being able to continue right before the battle that kills me is a great feature as I don't like backtracking from a recent save point and at the same time, I have the chance to change my setup before trying again. Only problem being I didn't do missions on the grassy plains when I was first there. The game felt quite a lot more difficult from there on. I ended up finding a good target to grind before continuing.
The battle design is good. I even like it enough to briefly consider grinding for platinum. In the end, the decision not to go for platinum was made easy when disaster struck my PS3 and I lost all my saves since my last backup 6 months ago together with any locked saves like Demon's Souls.
Seriously, for people who drag out playing their games over many months, make sure you backup often. My only saving grace is I usually play and finish games one by one. I haven't lost a bunch of saves for which I've progressed to the middle or something like that. I'm not pleased about losing saves, but at least it's not going to hinder me finishing those games.
My main complaint about FF13 is although I like linearity, I would very much prefer being able to change and configure team members far earlier than this game let me. Certain sections may feel better if they're shorter but overall, I feel fine and comfortable with this game.
Coincidentally, I was playing Xenogears again at the same time as I was playing FF13. Going through that game again made me think if those content are to be properly rendered in FF13 level of graphics and with the same attention to details, it's going to cost an awful lot more than FF13. In the old days, many little things like a cup of tea suddenly appearing in a character's hand were perfectly acceptable simplifications. It allowed for easier development. Nowadays, I think players generally expect a lot more details to be filled in and properly presented with nice animations, voice etc. It also reminded me how much more user friendly games have become in general (not just FF). Even games that aren't so linear as FF13 don't allow as much room for players to be stuck these days.