Finished the game yesterday on hard. Took me close to 70 hours since I did about half the substory missions (50) and a lot of the other optional stuff. Even on hard I never died once.
The amount of extra stuff in the game in insane. I'm playing the "New Adventure" mode where you get to keep everything you got, and I probably will put another 30 hours into the game before I'm bored.
It's one of my favorite PS3 games, although I still think Kenzan was more enjoyable. It's true that the graphics in the game can be not too appealing at times, and together with the minimal voice acting and cut-scenes makes it seem like the budget was on the low side. At least that means another installment is more likely!
It's an improvement over RgG2, but it's not fundamentally different. Satisfying fighting engine, and tons of interesting sidequests to do.
I did notice that the game wouldn't update some stats after a while (such as the total distance you've walked and the number of heat finishing moves you've done), and loading took much longer whenever I had a download in the background. Other than that, I haven't had any major bug (although in one of the kyabakura conversations they switched Kiryuu's and Saaya's lines!).