This was also my concern after reading the reviews on the first model. I'm not the world's fastest hand-writer so I found the device surprisingly snappy and the latency - while perceivable if paying close attention to it - hasn't really bugged me at all.
I love my RM2 for sketching and notes, but the eBook experience is like comically bad. It doesn't even get tabs right for me most of the time.
edit: looks like a recent update might have addressed this. time to give it another shot!