The game isn't bad, but isn't as great as FFVI or FFIX either. It certainly isn't as bad as some people are making it out to be.
Sure the game is extremely linear, but that has to do more with the audience and times we are in when people crave 6-8 hour shooters. Would the game be better if it was more open and had a deeper combat system similar to FFXII? Well as a fan of the series, hell yes it would be, but then would the game attract the same audience? I think SE was trying to capture a larger audience with this game (putting it on the lead HD console in the West (betrayal!), sponsoring the NBA All Star game, ect).
The game has a solid core, with a decent plot. Sure it has plenty of cliches, and some of the worst dialog I've ever seen in ANY RPG, but for the most part, the story makes sense and can be followed, which fixes a problem some previous FFs had.
I say go into the game with an open mind, knowing that there are several major issues with the core game, and try to just have fun. I know I did. In the end I think the core of the game is solid, and there are parts of brilliance, but if you can't try to enjoy the game or get past the obvious flaws (even though I think they are really only minor flaws), you probably won't enjoy it.