I've been utterly obsessed with Ar Tonelico Qoga over the last few days after taking a brief break. Once I start it generally sucks me in completely - for example, the BGM was stuck in my head on a loop while I was trying to get some sleep after a bit of a marathon session.
There are a few decision points during the game that affect how the remainder plays out - I've taken to keeping a pen and paper nearby to keep track of which save games reflect which choice. The worst part was when I ran out of time during a boss battle but the game continued as if it was one of those typical RPG story battles where you lose no matter what. Unfortunately I continued playing for 3 or 4 hours before going back to an earlier save to try the battle again - sure enough, with a better strategy and some upgraded super moves, the battle was won within the time allotted and the story changed appropriately. From what I gather, losing the battle leads to a bad ending while winning leads to a normal or good ending.
My main save is approaching the 40 hour mark now and the story seems to be going into the final stretch. I'm still loving the battle system, which is fortunate in a game of this length, and the number of extra things to do on the side makes a nice diversion as well.