It was frustrating during Volumes 4-6 because we were given only crumbs on his characterization. Most of it had to come from extrapolating his behavior by assessing the scenes they gave him.
Volume 4 allowed us to have a glimpse of his possible character, but he still remained illusive on how we can interpret him because Ozpin played a crucial part in that.
I think our biggest catch of his personality and concerned came in Volume 5 when he and Ruby talked in the dojo. We were finally able to see his doubts and inner turmoil. Furthermore, we even see how he came to start bonding with the others as shown when he grew upset when Ruby was hurt in the Volume 5 finale.
However, the biggest misstep with him is in Volume 6 when CRWBY cut out his inner journey after he left everyone. I'm glad we were able to get a JNR moment, but I wish we also were able to see what Oscar went through and how he managed to settle his doubts for a moment.
Volumes 7 and 8 are our biggest best chance to know who Oscar is as a person. We see him how he wants to distinguish himself away from Ozpin. Choosing to trust others and even risking himself in order to talk to Ironwood. We even see more of that growth in Volume 8 where he wants to talk to Salem's cadre rather than escape.
Unfortunately, his haters seem to dismiss his development in Volumes 7 and 8 which I think is a great shame. Regardless, I'm still plenty excited of what will happen next for him.
I like how they're doing the merging so far, but I would love to be surprised to find that Oscar, as we know him, remains relatively the same boy we came to love about him.