Lazy late update: I've finished Xenogears four days ago. Disc 2 was as short as I've feared, and while it took me ~10 hours to get to the end, actual gameplay took less than half or so (cutscenes galore),+- a couple of hours for preDeus grinding; I've upgraded only three Gears with partial Omega Setups.
As for OST, I was uninterested in majority of the tracks. The only pieces that truly caught my attention were mostly ambient or chorus/organ ones. That is, "Light from the Netherworld", "Ship of Regret and Sleep" and "Premonition". "One Who is Torn Apart" gets a special mention (damn this one is so good).
All my problems with it still stand, and some of them were only amplified with Disc 2. I can see the masterpiece in this one, yes, but it's just too unfinished and rushed to be one. If it had a proper development instead of a hellish one it got, maybe I would have loved it. As it is, though... it couldn't stand tall and shake the heavens for me. It's good even in halfbaked state, I give it that. But it could have been great.
P.S. And oh my, the English voiceover it the last cutscene is so cheesy. Extra cheesy.