I pre-order this, as I absolutely love the FF series of games. First impressions on turning it on were that the graphics are fantastic, as you'd expect from a 'next-gen' console.
Gameplay-wise, I believe they've got the system right this time. There's no running around during combat, like you have to do in FF12 (which I always hated), and the combat is actually pretty free-flowing. You only control one character, the other two work automatically depending on a 'program' you select for them (called a Paradigm, for example the medic paradigm will heal you, the relentless one will keep attacking, the commando one will get naked ... nvm).
You get a lot of cutscenes in the first two chapters, but that's Japanese games for you (not as bad as the MG series).
From what I can see, the game seems pretty deep, it's on three (3) xbox 360 discs, so it's fairly hefty. I personally recommend it.
The Xbox 360 version is going to feature compressed video and audio, presumably in an attempt to get as much content as it can on one DVD.
Despite the compression, the Xbox 360 version will still ship on multiple discs. Meanwhile, Final Fantasy XIII on PS3 will be uncompressed and resplendent on a single dual-layered Blu-ray disc. To give you a sense of how far ahead Blu-ray discs are, a dual-layered BD can hold 50GBs of data and a dual-layered DVD holds 9GB.
While the compressed nature of the 360 version will have very little effect on normal people, the fanboys are going to have a field day. This is a de facto victory for the Sony obsessives, even though their human eyes and ears won't be able to detect a real difference in quality between the two.