I have a few things to say on this topic. I don't know if people will still read this, or if it matters, but I feel like sharing my opinion anyway.
First off, I play with locked camera. When I started playing this game, the first thing I did was play the training mode, and locked camera is the default option in that mode. This definitely, and very heavily I might add, influenced my decision.
I have played other RTSs before, like Age of Empires and Warcraft III, where the camera is not locked and had no problems. Yet, I feel more comfortable playing on locked because that is how I learned to play THIS game. I have tried to learn unlocked for this game in the past, and it just feels odd to me in this game. We all must be creatures of habit, I guess.
I do not feel it hinders my gameplay too greatly as I play mainly bruisers. Whenever need to focus on action that is happening outside of my field of vision, I hit hotkey 'Y' (Toggle on/off camera lock) and drag the mini-map. Unfortunately, I know that because I play in this mode, there are certain champions that I may not be able to become proficient with.
I do have suggestions, if anyone is interested. First idea, remove locked as the default, especially in training mode. Second idea, add in a battle training that specifically focuses on camera management, like a mini-game wherein common situations for moving the camera great distances occur. Third idea, in the 'other options' tap in the settings, maybe there could be a 'tethered camera' or 'yo-yo camera' option. My idea of this third option would be, the camera is locked for the most part, but if you move your cursor to the edge of the screen, but only for a set duration before moving back its original positioning.