I don't know about that - the opening sections (after the excellent into as you mentioned), are very slow, especially when you just have Vaan and Penelo trawling about the Giza Plains etc. But I think it picks up big time from the Garamscythe Waterways - specifically when you get Fran and Balthier to form your first proper party. I really enjoy that level, and it gets even better when you meet Ashe too.
The prison and the lightworks aren't handled as well as I'd like (as the AI for Basch when he is a guest and his lack of equipment are very irritating, causing him to die constantly, when he's actually one of the hardest characters - not the best way to reintroduce the character!). And the soldiers armied with guns in the prison can be a real pain too.
I really love Ba'Gamnan and his villainous cronies, so I really enjoyed the whole jaunt into the mines and the scrap with the pirates. I could definately have lived without the 'Vaan pretends to be Basch' sequence, but other than that, I really enjoyed that section of the game, and it snowballs quickly into the superb jail break on the Leviathan. By that point, FF12 is on a real roll, and is part of why I love it so much.
I mean, Judge Ghis is in that section, and he's an awesome character! But yeah, I agree totally with Fight in that whilst I wasn't sure about FF12 when I bought it, I came to regard it as one of the very best Final Fantasys. (I got into it pretty quickly actually, but after the intro, that bit where you're just knocking about with Vaan and Penelo is a real pain barrier to be overcome!)
I still get the shakes remembering the epic, epic fight I had with Yiazmat. Took me a whole afternoon, but I finally got the swine in the end. 50 million HP - 50 frickin million!