From the reveiws I've read, and some games i've played, it seems that the issue of being overly linear in FF is that the combat system takes nearly 20 hours to get to play. Your fed little bits at a time, beat up some mobs, get new bits, beat up mobs with those new bits and repeat... for 20 hours. Then, after all that is said and done, your able to actually play the meat of the game and enjoy the hell out of it.
Really, this reminds me of the newest Bionic Commando game. I enjoyed the game immensely, however you didn't even start with a grapple arm. Once you got your arm, you couldn't perform any moves with it until you had unlocked or earned those abilities... okay. Well the pacing wasn't so horrid in that game that it would turn you off on the first walkthrough. Now, after beating the game and wanting to do walkthrough #2.... well I shut the damn thing off after 2 hrs because I couldn't do any of the moves etc that I was accustomed to kicking ass with.
The linear logic behind introducing a person to the game and forcing them to sit through every bit of that again on a second walkthrough really really sucks. The first time, maybe not so much (unless its 20 freakin hours!?!).
WRPG's are similarly linear to FF, however in WRPG's the combat system is typically static and the character levels, has a skill tree etc, and uses weapons/mods to increase their power. This style of RPG leads to a more "open-ended" feeling overall, as your character grows with you in the manner which you see fit (or in whichever order you get loot drops ha). Oh yeah, and 2nd and 3rd and 4th + walkthroughs are ALOT funner as a result as well.
In the end, it's less about the linear path of the story and more about the linear path of your character. Imagine having to play the entire damned tutorial on the hardest difficulty of a game on your 2nd walkthrough. That is too much of a forced progression IMO.