This is how I feel too. I keep bouncing off of them, but I really want to like them.
I'm guessing it's the top down camera that's the issue with lack of immersion.
The only CRPG I didn't bounce off of was Pathfinder: Wrath of the Righteous. Not 100% sure why that one clicked, but it might be the writing.
I think I got lucky and got one of the models with improved battery (Onyx Boox Page). I've been reading the Trigun manga on it for days now and it's only just getting to the point where I need to charge it finally.
But good point. Some of the older models might have worse battery life to consider. I only have a black and white model too. Color might use more battery.
I also read some things in the languages I'm trying to learn, and this feature is essential for translating words I don't know yet.
Plus, the backlight (adjusted for warmth so as not to keep me up) lets me read in bed with the light off and I don't have to get up to turn it off when I'm done.
I was very pro only real books for a while, and still am a fan of a real book, but the quality of life features of e-readers eventually sold me. Especially because night is one of the few times I can read.